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Serine

Serine is a non-essential, proteinogenic α-amino acid with the chemical formula C₃H₇NO₃ and the systematic name 2-amino-3-hydroxypropanoic acid, featuring a polar, uncharged side chain consisting of a hydroxymethyl group (-CH₂OH) that enables hydrogen bonding and phosphorylation in proteins.^[1] It exists primarily as the L-enantiomer in biological systems and is one of the 20 standard amino acids incorporated into proteins, often comprising 5–10% of the total amino acid content in many proteins by weight.^[1] Physically, L-serine appears as a white crystalline powder with a melting point of 228 °C (decomposing) and high solubility in water (approximately 425 g/L at 25 °C), but it is insoluble in non-polar solvents like ether and benzene.^[1] In humans and other organisms, L-serine is biosynthesized endogenously through the phosphorylated pathway, which branches from glycolysis and converts the glycolytic intermediate 3-phosphoglycerate into L-serine via three key enzymes: 3-phosphoglycerate dehydrogenase (PHGDH), which oxidizes 3-phosphoglycerate to 3-phosphohydroxypyruvate using NAD⁺; phosphoserine aminotransferase (PSAT), which transaminates the intermediate to 3-phosphoserine using glutamate as the amino donor and pyridoxal phosphate (PLP) as a cofactor; and phosphoserine phosphatase (PSP), which hydrolyzes 3-phosphoserine to yield L-serine.^[2] This de novo synthesis is particularly active in the brain, where astrocytes and glial cells supply L-serine to neurons for essential functions, and disruptions in this pathway are linked to neurological disorders such as serine deficiency syndromes.^[2] Alternatively, serine can be derived from dietary sources or interconverted with glycine through serine hydroxymethyltransferase in the folate-dependent one-carbon metabolism cycle.^[1] Biochemically, serine plays critical roles beyond protein structure, serving as a precursor for the synthesis of other amino acids (glycine and cysteine), nucleotides (purines and pyrimidines), phospholipids (including sphingolipids), and the neurotransmitter D-serine, which acts as a co-agonist for NMDA receptors in synaptic plasticity and learning.^[1] Its hydroxyl group facilitates post-translational modifications like O-glycosylation and phosphorylation, influencing enzyme activity and signaling pathways, while in metabolism, serine contributes to one-carbon units for methylation reactions, epigenetics, and antioxidant defense via glutathione production.^[1] Dysregulation of serine metabolism is implicated in diseases including cancer, where upregulated biosynthesis supports rapid cell proliferation, and neurodegenerative conditions like Alzheimer's.^[2]

Chemical Properties

Structure and Nomenclature

Serine is an α-amino acid with the molecular formula C₃H₇NO₃ and a side chain consisting of a hydroxymethyl group (-CH₂OH) attached to the central α-carbon atom, which also bears an amino group (-NH₂) and a carboxyl group (-COOH). This structure positions serine as a non-essential amino acid in human metabolism, with the hydroxyl group on the side chain enabling hydrogen bonding interactions. The systematic IUPAC name for the naturally occurring enantiomer is (2S)-2-amino-3-hydroxypropanoic acid, commonly abbreviated as Ser or S in biochemical contexts. In the standard genetic code, serine is encoded by the six codons UCU, UCC, UCA, UCG, AGU, and AGC.^[3] Serine exhibits chirality at the α-carbon, resulting in two enantiomers: L-serine, which has the (S) absolute configuration and predominates in biological systems including proteins, and D-serine, which has the (R) configuration and occurs less frequently.^[4] The stereochemistry can be visualized in a Fischer projection for L-serine, where the carboxyl group is placed at the top, the amino group projects to the left, the hydrogen to the right, and the -CH₂OH side chain at the bottom:

   COOH
H₂N─C─H
  CH₂OH
   COOH
H₂N─C─H
  CH₂OH

In three-dimensional terms, the α-carbon adopts a tetrahedral geometry, with the substituents arranged such that the priorities for (S) configuration follow the Cahn-Ingold-Prelog rules: carboxyl (highest), side chain, amino, and hydrogen (lowest). The ionization behavior of serine is characterized by pKa values of 2.21 for the α-carboxyl group, 9.15 for the α-amino group, and approximately 13.0 for the side chain hydroxyl group.^[5] These values reflect its zwitterionic form at physiological pH, where the side chain remains protonated and uncharged. Serine is classified as a polar, uncharged, hydrophilic amino acid, owing to the polar hydroxyl group in its side chain that facilitates hydrogen bonding with water and other polar molecules.^[6]

Physical and Chemical Properties

Serine appears as a white crystalline powder.^[7] Its molecular weight is 105.09 g/mol.^[7] The compound has a melting point of 228 °C, at which it decomposes.^[7] Serine exhibits high solubility in water, approximately 425 g/L at 25 °C, while it is practically insoluble in ethanol, ether, and benzene.^[7] The L-enantiomer displays optical activity, with a specific rotation [α]_D of -6.83° at 20 °C (1.5 g in 15 g aqueous solution).^[7] Serine is hygroscopic and remains stable under neutral conditions.^[8] However, it is prone to racemization in strong acidic or basic environments.^[9] At physiological pH, serine exists predominantly in its zwitterionic form due to the pKa values of its carboxyl (approximately 2.2) and amino (approximately 9.2) groups.^[7] The polar hydroxyl and amino groups enable extensive hydrogen bonding, contributing to its solubility and interactions in aqueous media.^[7]

Natural Occurrence

In Biological Systems

Serine is classified as a non-essential amino acid, meaning it can be synthesized by organisms from other metabolic intermediates, and is ubiquitously present across all three domains of life—bacteria, archaea, and eukarya—as a fundamental building block of proteins and other biomolecules.^[10]^[11] In eukaryotic proteins, serine typically accounts for 5-10% of total amino acid residues, reflecting its high abundance and versatility in polypeptide structures. It is particularly enriched in certain specialized proteins, such as silk fibroin from Bombyx mori, where it constitutes up to 12% of the composition, contributing to the material's structural integrity.^[12] Additionally, serine predominates in phosphoproteins, serving as the primary site for phosphorylation and comprising the majority of such modifications, which regulate enzymatic activity and signaling pathways.^[13] Serine's distribution extends to key cellular structures and organelles. In bacteria, it is incorporated into peptidoglycan, the primary component of the cell wall, particularly in interpeptide bridges of species like Staphylococcus epidermidis, where it links glycan strands to maintain structural rigidity.^[14] In eukaryotes, serine is a component of myelin sheath proteins. It is also present in mitochondrial proteins, contributing to cellular homeostasis.^[15] Serine exists in both free and bound forms within cells. The L-enantiomer predominates as free amino acid in the cytoplasm, with tissue concentrations typically around 600 nmol/g wet weight, facilitating rapid metabolic flux.^[16] In contrast, the D-enantiomer is enriched in the extracellular space of the brain, reaching concentrations of approximately 5 μM in regions like the prefrontal cortex and up to higher levels in specific microenvironments, where it modulates synaptic activity.^[17] The evolutionary conservation of serine underscores its ancient origins. It is encoded by six universal codons—UCU, UCC, UCA, UCG, AGU, and AGC—preserved across nearly all known genetic codes, reflecting minimal variation despite billions of years of divergence.^[18] This stability, coupled with serine's simple hydroxymethyl side chain, supports hypotheses that it was among the earliest amino acids integrated into primordial translation systems during the transition from an RNA world, where basic residues likely facilitated initial peptide-RNA interactions.^[19]

Dietary and Environmental Sources

Serine is primarily obtained through dietary sources rich in proteins, including animal products such as meat, eggs, and dairy, as well as plant-based foods like soy, nuts, and certain vegetables. Chicken breast provides approximately 1.2 g of serine per 100 g, while beef contains about 1.3 g per 100 g. Eggs, particularly dried egg whites, offer up to 5.6 g per 100 g, and various cheeses, such as Romano, supply around 1.8 g per 100 g. Soy protein isolate is a notable plant source at 4.6 g per 100 g, with nuts like peanuts contributing about 1.7 g per 100 g in low-fat flour form; vegetables including potatoes and beans provide smaller but relevant amounts, typically 0.8–1.2 g per 100 g.^[20]^[21]^[22] As a non-essential amino acid, serine lacks a specific recommended daily allowance, but typical intake in a Western diet ranges from 3 to 5 g per day, derived mainly from meat, poultry, fish, grains, and dairy. Plant-based diets may yield higher effective levels through precursors that support endogenous synthesis.^[23] In environmental contexts, serine forms abiotically and has been identified in extraterrestrial sources, such as the Murchison meteorite, where it comprises 1–2% of the total amino acids, suggesting prebiotic synthesis pathways. On Earth, abiotic production occurs in submarine hydrothermal vents via mechanisms like the Strecker synthesis, involving reactions of aldehydes, hydrogen cyanide, and ammonia under high-temperature, high-pressure conditions.^[24]^[25]

Biosynthesis and Synthesis

Biological Biosynthesis Pathways

In biological systems, L-serine is primarily synthesized via the phosphorylated pathway, starting from the glycolytic intermediate 3-phosphoglycerate. This pathway involves three main enzymes: 3-phosphoglycerate dehydrogenase (PHGDH), which oxidizes 3-phosphoglycerate to 3-phosphohydroxypyruvate using NAD⁺ as a cofactor; phosphoserine aminotransferase (PSAT1), which transfers an amino group from glutamate to 3-phosphohydroxypyruvate, forming 3-phosphoserine, with pyridoxal phosphate (PLP) as a cofactor; and phosphoserine phosphatase (PSPH), which dephosphorylates 3-phosphoserine to produce L-serine.^[2] This pathway is highly active in the liver, kidney, and brain, where it supports one-carbon metabolism and neurotransmitter synthesis. An alternative route is the conversion of glycine to L-serine via serine hydroxymethyltransferase (SHMT), which catalyzes the reversible transfer of a hydroxymethyl group from 5,10-methylenetetrahydrofolate to glycine in a PLP-dependent reaction. This glycine-dependent pathway is prominent in mitochondria and cytosol, integrating with folate metabolism.^[1] Industrial biological production often employs enzymatic conversions or microbial fermentation. Enzymatic methods use serine hydroxymethyltransferase or serine aldolase to convert glycine (with formaldehyde) to L-serine in vitro, achieving high stereoselectivity. Microbial fermentation with engineered strains of Escherichia coli or Corynebacterium glutamicum, utilizing glucose or other renewable feedstocks, can produce L-serine at titers exceeding 50 g/L under optimized conditions. These processes yield pharmaceutical-grade L-serine with >99% chemical purity and >99% enantiomeric excess.^[26]

Chemical Synthesis Methods

One classical method for synthesizing serine involves the Strecker synthesis, where glycolaldehyde reacts with ammonia and hydrogen cyanide to form an α-aminonitrile intermediate, which is subsequently hydrolyzed to yield DL-serine. This approach, first applied to serine in the early 20th century, provides racemic product but serves as a foundational route for laboratory-scale preparation.^[27] Another established chemical route utilizes chloroacetic acid, ammonia, and formaldehyde, proceeding via the formation of an imine intermediate followed by cyclization and hydrolysis to produce DL-serine. The key reaction is represented as:

\text{ClCH}_2\text{COOH} + \text{NH}_3 + \text{HCHO} \rightarrow \text{HOCH}_2\text{CH(NH}_2\text{)COOH} + \text{HCl}

This method, reported in the 1920s, achieves moderate yields and has been adapted for larger-scale production of the racemate.^[28] For enantiopure L-serine, stereoselective synthesis employs asymmetric hydrogenation of protected dehydroserine derivatives, such as Z- or E-β-hydroxy-α-acetamidocinnamic acid esters, using rhodium complexes with chiral DuPHOS ligands. These reactions typically deliver L-serine with >99% enantiomeric excess (ee) after deprotection, enabling pharmaceutical-grade material suitable for peptide synthesis.^[29] Global production of L-serine is estimated at approximately 3,000 tons per year as of 2022, driven by applications in pharmaceuticals and cosmetics.^[30]

Chemical Reactions

Side Chain Reactivity

The side chain of serine, consisting of a hydroxymethyl group (-CH₂OH), imparts nucleophilic reactivity to the molecule due to the oxygen atom's lone pairs, allowing it to act as a nucleophile in forming esters and ethers with electrophilic reagents such as acyl chlorides or alkyl halides.^[31] This nucleophilicity also enables non-enzymatic O-phosphorylation of the hydroxyl group using ATP, particularly when facilitated by divalent metal ions like Mn²⁺ under neutral or mildly basic conditions, yielding a phosphoserine derivative.^[32] A key reaction involving the side chain is base-catalyzed β-elimination, where the hydroxyl group facilitates dehydration to form dehydroalanine, an unsaturated amino acid residue, through elimination of water from the β-position. This process, often promoted by strong bases or in peptide contexts with activated leaving groups, proceeds as follows:

\ce{HO-CH2-CH(NH2)-COOH ->[base] CH2=C(NH2)-COOH + H2O}

Such transformations are utilized in synthetic chemistry to introduce α,β-unsaturated functionalities.^[33] Oxidative reactions of the side chain hydroxyl group demonstrate its susceptibility to cleavage and transformation. Treatment with sodium periodate (NaIO₄) leads to oxidative cleavage of the Cα-Cβ bond, producing formaldehyde (from the side chain), glyoxylic acid, and ammonia as the primary products.^[34] Chemical oxidation under harsher conditions can further convert serine derivatives to hydroxypyruvate or glyoxylate, highlighting the group's vulnerability to oxidants that target the alcohol functionality. In peptide and organic synthesis, the reactive hydroxyl is routinely protected to avoid side reactions; common strategies include silylation to form the tert-butyldimethylsilyl (TBDMS) ether, which is stable to basic conditions and removed by fluoride ions, or conversion to a benzyl ether, removable by hydrogenolysis.^[35] The side chain's pH-dependent behavior stems from the hydroxyl group's pKₐ of approximately 13, rendering deprotonation negligible at physiological pH but enabling strong hydrogen bonding as a donor in neutral environments.

Synthetic and Biochemical Transformations

In peptide synthesis, serine is commonly activated for coupling by forming an active ester intermediate using N,N'-dicyclohexylcarbodiimide (DCC), which generates an O-acylisourea that facilitates amide bond formation with the incoming amine without requiring additional additives in many cases.^[36] The Fmoc-protected form, Fmoc-Ser-OH, serves as a key building block in solid-phase peptide synthesis, where it is incorporated via activation with reagents like HBTU or DIC, followed by Fmoc deprotection with piperidine to enable chain elongation while minimizing side reactions at the unprotected hydroxyl group.^[37] Industrially, serine is utilized in the synthesis of mild, biodegradable surfactants based on amino acids, which exhibit good foaming and emulsifying properties in personal care formulations.^[38] Regarding stereochemistry, enzymatic transformations of serine, such as those mediated by dehydratases or transaminases, exhibit high specificity for the L-enantiomer with retention of configuration at the α-carbon, owing to the chiral active sites that exclude D-serine.^[39] In contrast, chemical reactions like nucleophilic substitutions on serine-derived esters often proceed via SN2 mechanisms, resulting in inversion of stereochemistry at the reactive center, as seen in the synthesis of modified amino acid analogs.^[40]

Biological Functions

Role in Proteins

Serine is incorporated into proteins during translation via six codons: UCU, UCC, UCA, UCG (collectively UCN), AGU, and AGC (AGY), making it one of the amino acids with the most degenerate genetic code. This dual codon set reflects evolutionary adaptations for precise control of serine incorporation, as single-nucleotide substitutions cannot interconvert UCN and AGY groups. In the human proteome, serine accounts for approximately 8.1% of all amino acid residues, with codon usage varying by tissue and organism; for instance, AGC is the most frequent serine codon in humans at 19.5 per thousand, while UCG is the least at 4.4 per thousand.^[41] The polar hydroxyl group of serine's side chain enables it to serve as both a hydrogen bond donor and acceptor, stabilizing secondary structures such as α-helices and β-turns. In α-helices, serine residues preferentially form intra-helical hydrogen bonds between their Oγ atom and the backbone carbonyl oxygen four residues upstream (i to i-4), enhancing helical stability and often capping helix termini. Serine also promotes β-turns by facilitating tight turns through side-chain-backbone interactions, and its hydrophilic nature positions it predominantly in solvent-exposed regions, contributing to protein solubility and surface interactions. Additionally, serine can induce slight bends in α-helices via gauche-minus (g⁻) conformations of its χ₁ dihedral angle, influencing local flexibility.^[42]^[43] Serine undergoes post-translational O-glycosylation, primarily involving the attachment of N-acetylgalactosamine (GalNAc) to its side-chain hydroxyl group, forming GalNAc-Ser linkages that modulate protein folding, stability, and cellular trafficking. This modification is less prevalent on serine than on threonine due to steric and enzymatic preferences, with threonine substrates glycosylated up to several-fold more efficiently by UDP-GalNAc transferases across pH ranges and enzyme sources. In comparison, tyrosine undergoes rarer O-glycosylation, mainly in specific contexts like nuclear proteins. Serine phosphorylation, a key modification for signaling, occurs on its hydroxyl group but is covered in non-metabolic roles. In antibodies, serine residues are enriched in complementarity-determining regions (CDRs), where AGY codons predominate beyond random expectations, supporting structural diversity and flexibility for antigen recognition. For example, in immunoglobulin variable regions, serine facilitates hydrogen bonding and conformational adaptability in CDR loops. In enzymes, serine is critical in the active site of serine proteases, forming the catalytic triad with histidine and aspartic acid; the serine's nucleophilic hydroxyl attacks peptide bonds, enabling hydrolysis with rate enhancements up to 10¹⁰-fold, as dissected through site-directed mutagenesis studies.^[44]^[45] Serine is frequently conserved in flexible loops, where its hydrogen-bonding capacity maintains local dynamics and inter-residue interactions essential for protein function. Such positions often exhibit evolutionary conservation to preserve loop flexibility and solvent interactions. Mutations like Ser to Ala disrupt these hydrogen bonds, typically reducing protein stability by 1-3 kcal/mol and altering folding kinetics—Ala accelerates folding but Ser slows unfolding to enhance stability—though effects vary by context, sometimes yielding moderate stabilization at the cost of catalytic efficiency.^[46]^[47]

Metabolic Roles

Serine serves as a central hub in cellular metabolism, acting as a precursor for the biosynthesis of several biomolecules. Through the enzyme serine hydroxymethyltransferase (SHMT), L-serine is converted to glycine while donating a one-carbon unit to tetrahydrofolate, supporting folate-dependent one-carbon metabolism essential for nucleotide synthesis, methylation reactions, and epigenetics.^[48] This pathway also facilitates the production of cysteine via the transsulfuration route, where serine-derived glycine combines with methionine metabolites. Additionally, serine contributes to the synthesis of sphingolipids and phospholipids, incorporating into ceramide and phosphatidylserine, which are crucial for membrane structure and signaling. In nucleotide metabolism, serine provides carbon atoms for purine biosynthesis and indirectly supports pyrimidines through one-carbon units. Dysregulation of these metabolic roles is linked to cancer and metabolic disorders, where altered serine flux affects cell proliferation and redox balance.^[49]

Non-Metabolic Roles

Serine plays critical roles in cellular signaling and regulation through post-translational modifications and neuromodulatory functions. One prominent non-metabolic role involves O-phosphorylation on serine residues within proteins, catalyzed by serine/threonine kinases such as protein kinase A (PKA) and mitogen-activated protein kinases (MAPKs).^[50] These kinases target the hydroxyl group of serine's side chain, adding a phosphate group that alters protein conformation, activity, and interactions. In eukaryotic cells, serine phosphorylation accounts for approximately 86.4% of all phosphorylation events, underscoring its prevalence in regulatory networks.^[51] For instance, phosphorylation of glycogen synthase by GSK-3 and other kinases on multiple serine residues inhibits its activity, thereby controlling glycogen synthesis in response to hormonal signals like insulin and glucagon.^[52] Beyond protein modification, D-serine, the enantiomer of L-serine, functions as an endogenous co-agonist at N-methyl-D-aspartate (NMDA) receptors in the central nervous system. Produced primarily by astrocytes via serine racemase, D-serine binds to the glycine site of NMDA receptors, enhancing their activation by glutamate and facilitating calcium influx critical for synaptic transmission.^[53] This co-activation modulates synaptic plasticity, including long-term potentiation (LTP), which is essential for learning and memory formation. Dysregulation of D-serine levels, often reduced in the prefrontal cortex and hippocampus, has been implicated in schizophrenia, where it contributes to NMDA receptor hypofunction and cognitive deficits; supplementation studies suggest potential therapeutic benefits in restoring synaptic function.^[54] In programmed cell death, serine proteases such as granzyme B mediate key steps in apoptosis. Granzyme B, released from cytotoxic T lymphocytes and natural killer cells, is a serine protease featuring the canonical Ser-His-Asp catalytic triad in its active site, which enables nucleophilic attack on peptide bonds.^[55] During the execution phase of apoptosis, granzyme B enters target cells via perforin pores and cleaves substrates after aspartic acid residues, activating downstream caspases and Bid to trigger mitochondrial outer membrane permeabilization, cytochrome c release, and caspase cascade amplification.^[56] This pathway ensures rapid dismantling of cellular structures, distinguishing it from other death mechanisms. Serine residues in proteins also participate in non-enzymatic glycation via the Maillard reaction, leading to the formation of advanced glycation end-products (AGEs). In this process, the side chain hydroxyl or alpha-amino group of serine reacts with reducing sugars like glucose, forming initial Schiff bases that rearrange into Amadori products and eventually stable, cross-linking AGEs such as carboxymethyl-lysine.^[57] These modifications accumulate in long-lived proteins, contributing to tissue stiffening and inflammation in aging and diabetes, though serine-specific glycation is less common than on lysine or arginine residues.^[58] Recent research highlights serine's involvement in maintaining redox balance through de novo synthesis pathways, particularly in mitochondrial disorders. In cellular models of mitochondrial dysfunction, such as those with respiratory chain defects, upregulated de novo serine biosynthesis via phosphoglycerate dehydrogenase (PHGDH) supports NADPH production and glutathione recycling, mitigating oxidative stress and preserving mitochondrial biogenesis.^[59] Studies from 2024–2025 demonstrate that this pathway is protective in macrophages and other cells, where serine-derived one-carbon metabolism buffers reactive oxygen species (ROS) accumulation, potentially offering therapeutic targets for mitochondrial diseases like Leigh syndrome.^[60]

Clinical and Research Aspects

Health Implications and Disorders

Serine deficiency is rare but has been associated with peripheral neuropathy in conditions like diabetes, where low levels of serine and glycine contribute to nerve damage and pain. In 2023 mouse studies, diabetic models exhibited serine and glycine deficiencies that heightened the risk of peripheral neuropathy, with symptoms including impaired nerve function and sensory deficits.^[61]^[62] Serine deficiency syndromes arise from genetic disruptions in its biosynthesis pathway, such as mutations in the PHGDH gene encoding phosphoglycerate dehydrogenase, leading to congenital microcephaly, psychomotor retardation, and seizures. These autosomal recessive disorders impair L-serine production, resulting in neurological phenotypes that can be partially mitigated by supplementation. Additionally, serine deficiency disrupts the one-carbon metabolic cycle, where serine serves as the primary donor for homocysteine remethylation, potentially elevating homocysteine levels and contributing to vascular and neurological complications.^[63]^[64]^[65] Excess D-serine exhibits neurotoxicity in amyotrophic lateral sclerosis (ALS) models, where elevated levels enhance glutamate-mediated excitotoxicity and motoneuron degeneration. In contrast, L-serine is generally safe at high doses, with clinical trials demonstrating tolerability up to 30 g/day in ALS patients without significant adverse effects.^[66]^[67]^[68] Low serine levels have been linked to Alzheimer's disease (AD), particularly through impaired L-serine biosynthesis in astrocytes, which reduces D-serine production and NMDA receptor function, exacerbating cognitive decline.^[69] In tumors, high serine flux supports rapid proliferation, rendering many cancer cells "serine-addicted" and dependent on upregulated biosynthesis for nucleotide and lipid synthesis.^[70] Normal plasma serine concentrations range from 100 to 200 μM in healthy individuals, serving as a diagnostic benchmark for serine biosynthesis deficiencies. Separately, hereditary sensory and autonomic neuropathy type 1 (HSAN1) arises from gain-of-function mutations in serine palmitoyltransferase (SPT) subunits, such as SPTLC1, leading to production of toxic deoxysphingolipids and resulting in sensory loss and ulcers. Genetic testing for these mutations is essential for HSAN1 diagnosis.^[71]^[72]^[73]

Therapeutic Potential and Recent Studies

L-serine supplementation shows promise in mitigating serine-related disorders. In ALS, phase I/II trials (as of 2020) indicate that doses up to 30 g/day are well-tolerated and may slow functional decline by countering protein misfolding and excitotoxicity.^[74] For HSAN1, randomized trials (2019) demonstrated that high-dose L-serine reduces neurotoxic deoxysphingolipids and slows neuropathy progression.^[75] In diabetic neuropathy models, serine supplementation (2023) alleviated nerve damage in mice.^[61] For AD, preclinical studies (2020) suggest L-serine restores synaptic function and cognition in mouse models via enhanced D-serine/NMDA signaling.^[69] Recent research (as of 2024) highlights L-serine's role in off-label ALS treatments, potentially via one-carbon metabolism support, though larger trials are needed. A 2023 review underscores its neuroprotective potential across neurodegenerative diseases.^[76]^[77]

References

[1]
L-Serine
### Summary of L-Serine from PubChem
[2]
https://doi.org/10.1007/s00018-020-03574-z
[3]
codons and amino acids
Genetic code. NOTE - starting VarNomen version 3 the '*' is used to indicate ... Serine, AGC, AGT, TCA, TCC, TCG, TCT. T, Thr, Threonine, ACA, ACC, ACG, ACT.Missing: source | Show results with:source
[4]
D-Serine
- **IUPAC Name**: (2R)-2-amino-3-hydroxypropanoic acid
[5]
Ch27 pKa and pI values - University of Calgary
pKa1= α-carboxyl group, pKa2 = α-ammonium ion, and pKa3 = side chain group. ... Serine, 2.21, 9.15, ---, 5.68. Threonine, 2.09, 9.10, ---, 5.60. Tyrosine, 2.20 ...
[6]
Serine - an overview | ScienceDirect Topics
Serine is defined as a polar, very weakly acidic amino acid that is uncharged at neutral pH, capable of forming hydrogen bonds and exhibiting high solubility.
[7]
L-Serine | C3H7NO3 | CID 5951 - PubChem - NIH
Serine is classified as a nutritionally non-essential amino acid. Serine is critical for the production of the body's proteins, enzymes and muscle tissue.
[8]
Hygroscopicity of amino acids and their effect on the water uptake of ...
Sep 10, 2020 · In this work, the hygroscopic properties of three amino acids, including aspartic acid, glutamine, and serine, as well as their mixtures ...
[9]
Method for racemization of optically active serine - Google Patents
Based on such research, it has been found that optically active serine can be racemized specifically when it is treated with aqueous alkaline solution in the ...Missing: hygroscopic | Show results with:hygroscopic
[10]
L-Serine: a Naturally-Occurring Amino Acid with Therapeutic Potential
Although L-serine is generally classified as a non-essential amino acid, it is probably more appropriate to term it as a "conditional non-essential amino acid ...
[11]
Genome-wide survey of prokaryotic serine proteases: Analysis of ...
Nov 19, 2008 · Serine proteases are one of the most abundant groups of proteolytic enzymes found in all the kingdoms of life.
[12]
Molecular Structure and Potential of Silk Fibroin as a Biomaterial
Sep 8, 2025 · The amino acid composition of Bombyx mori silk fibroin is predominantly glycine (43%), alanine (30%), and serine (12%). The hydrophobic ...Missing: eukaryotes | Show results with:eukaryotes
[13]
Phosphoprotein analysis: from proteins to proteomes
Jul 19, 2006 · Phosphorylation is a key reversible modification occurring mainly on serine, threonine and tyrosine residues that can regulate enzymatic ...
[14]
VII. Incorporation of Serine and Glycine into Interpeptide Bridges in ...
The peptidoglycan of Staphylococcus epidermidis contains serine and glycine in the interpeptide bridges. A particulate enzyme system has been obtained which ...
[15]
L-Serine, an Endogenous Amino Acid, Is a Potential Neuroprotective ...
Sep 6, 2021 · Activation of Akt by L-serine promotes the proliferation and survival of NSCs after brain injury, which plays an important role in myelin ...L-Serine And D-Serine · L-Serine Decreases... · L-Serine Improves Cerebral...<|separator|>
[16]
Serine Availability Influences Mitochondrial Dynamics and Function ...
Comparative Metabolomics Reveals that Serine Deprivation Compromises Mitochondrial Fatty Acid Metabolism. Serine deprivation reduces cell proliferation in ...
[17]
Free d-serine concentration in normal and Alzheimer human brain
There was no significant difference between the two brains. In normal brain, l- and d-serine concentrations were 666 ± 222 and 66 ± 41 nmol/g of wet tissue, ...Missing: cytoplasm | Show results with:cytoplasm
[18]
D-Serine as a putative glial neurotransmitter - PMC - PubMed Central
Studies by Hashimoto and colleagues (Hashimoto et al., 1995) indicate that extracellular concentrations of D-serine in the brain are ~5 μM, only about 1% of the ...
[19]
Evolution of the genetic code; Evidence from serine codon ... - PNAS
Nov 9, 2020 · Among the 20 amino acids, three of them—leucine (Leu), arginine (Arg), and serine (Ser)—are encoded by six different codons.Missing: source | Show results with:source
[20]
Clues to tRNA Evolution from the Distribution of Class II tRNAs and ...
Also, serine codons are found not only in the bottom right-hand corner of the genetic code table next to those for glycine and aspartic acid, but also in the ...
[21]
Treatment with amino acids in serine deficiency disorders - PubMed
Serine deficiency disorders are rare defects in the biosynthesis of the amino acid L-serine. At present two disorders have been reported: 3-phosphoglycerate ...
[22]
Nutrition Facts for Chicken Breast (Cooked)
100 grams (100g), 1 gram (1g), Add Custom Size. Compare ... Serine, 1222mg. Data Source. Chicken Breast (Cooked). User EnteredOmega-6 data ...
[23]
Serine in Meat - FitAudit
Serine in Meat ; 6, Beef, 1.27g ; 7, Beef liver, 1.27g ; 8, Antelope meat, 1.24g ; 9, Pork spleen, 1.23g ...
[24]
Serine Rich Foods - Medindia
Find Foods Highest in Serine (per 100 gram Serving) · 1. Egg, white, dried, stabilized, glucose reduced (6.159g) · 2. Egg, white, dried, powder, stabilized, ...
[25]
Serine metabolism in aging and age-related diseases - PMC
SM is found in animal cell membranes, particularly in the myelin sheath that encases some nerve cell axons and in plasma lipoproteins [54]. SM plays a critical ...
[26]
A new family of extraterrestrial amino acids in the Murchison meteorite
Apr 4, 2017 · Even though it was identified from Antarctic CR meteorites, this study revealed the first occurrence of isoserine in the Murchison meteorite.
[27]
Thermodynamics of Strecker synthesis in hydrothermal systems
The potential for Strecker synthesis to produce biomolecules (amino and hydroxy acids) from starting compounds (ketones, aldehydes, HCN and ammonia) in such ...Missing: serine vents
[28]
High-yield production of l-serine through a novel identified exporter ...
May 29, 2020 · This study provides a novel target for l-serine and l-threonine export engineering as well as a new global transcriptional regulator NCgl0581 in C. glutamicum.
[29]
Enzymes acting on peptides containing d-amino acid - ScienceDirect
Mainly microorganisms but only a few higher organisms are presently known to express enzymes that hydrolyze peptides containing d-amino acids.
[30]
dl-Serine - Organic Syntheses Procedure
Serine has been prepared by the Strecker method from glycol aldehyde and from ethoxyacetaldehyde,, by the condensation of ethyl formate with ethyl ...
[31]
Serine: Definition, Structure, Benefits, Types and Uses - BOC Sciences
Serine, also known as 2-amino-3-hydroxypropanoic acid, is a neutral aliphatic amino acid that contains a hydroxyl group.
[32]
Serine - an overview | ScienceDirect Topics
A hydroxyl group at the end of the side chain makes serine more polar than alanine, yet uncharged at pH 7. ... The —OH group of serine has a weakly acidic pK′ of ...
[33]
Nonenzymatic phosphorylation of tyrosine and serine by ATP is ...
We have observed that peptides and proteins are non-enzymatically phosphorylated at tyrosine and serine by ATP when heated in the presence of MnCl2 at neutral ...
[34]
Synthesis of dehydroalanine peptides from .beta. - ACS Publications
... Serine Derivative and β-Elimination. Chemistry Letters 1994, 23 (7) , 1301-1304. https://doi.org/10.1246/cl.1994.1301. Karen Goodall, Andrew F. Parsons. New ...
[35]
Oxidation of L-serine and L-threonine by bis(hydrogen periodato ...
The oxidation products of the amino acids have been identified as ammonia, glyoxylic acid and aldehyde (formaldehyde for serine and acetaldehyde for threonine).
[36]
Protection of the Hydroxyl Group in Peptide Synthesis - ScienceDirect
Proper handling of hydroxyamino acids is important in peptide synthesis, but the need for protecting groups is uncertain, and side reactions can occur. The ...
[37]
Epimerisation in Peptide Synthesis - PMC - PubMed Central - NIH
One carbodiimide-based coupling reagent is DCC (N,N′-dicyclohexylcarbodiimide) (Figure 5). Activation of the carboxylic group using DCC produces ortho-acylurea, ...
[38]
Facile synthesis of glycosylated Fmoc amino acid building blocks ...
A glycosylated amino acid building block is easily introduced into a solid phase peptide synthesis using peptide chemistry. ... Fmoc-Ser-OH (0.01 mmol) and ...
[39]
Reconstruction of cysteine biosynthesis using engineered ... - Nature
Jan 29, 2018 · The first step of cysteine synthesis is catalyzed by serine acetyltransferase, produced by the gene cysE. Serine acetyltransferase converts ...
[40]
Glycine Hydroxymethyltransferase - an overview - ScienceDirect.com
Glycine Hydroxymethyltransferase is an enzyme that plays a key role in the biosynthesis of glycine by converting l-serine to glycine.
[41]
KEGG ENZYME: 4.3.1.17
L-serine = pyruvate + NH3 (overall reaction) [RN:R00220]; (1a) L-serine = 2-aminoprop-2-enoate + H2O [RN:R00590]; (1b) 2-aminoprop-2-enoate = 2-iminopropanoate ...<|separator|>
[42]
Characteristics of hepatic serine-pyruvate aminotransferase in ...
Mar 1, 1977 · The reverse transamination activity, with hydroxypyruvate and alanine as subtrates, was lower than with serine and pyruvate for both species.
[43]
D-Serine inhibits serine palmitoyltransferase, the enzyme ... - PubMed
May 26, 2000 · ... sphingolipid biosynthesis, catalyzes condensation of palmitoyl coenzyme A and L-serine to produce 3-ketodihydrosphingosine (KDS). For ...Missing: synthesis | Show results with:synthesis
[44]
The Relationship Between the Structure and Properties of Amino ...
Dec 30, 2012 · Two series of surfactants based on glycine and serine were synthesized with aproic acid, octanoic acid, decanoic acid, dodecanoic acid, ...
[45]
D-Serine: Potential Therapeutic Agent and/or Biomarker ... - Frontiers
D-Serine is a potent coagonist at the N-methyl-D-aspartate (NMDA) glutamate receptor and appears to have a major modulatory role in NMDA receptor-mediated ...Abstract · Formation and Catabolism of... · Clinical Studies With D-Serine...
[46]
l-Serine Catabolism via an Oxygen-Labile l-Serine Dehydratase Is ...
SdaA catalyzes the deamination of serine to pyruvate and ammonia, both of which can be readily assimilated. Although many serine dehydratases also deaminate ...Missing: NH3 | Show results with:NH3
[47]
Multigram-Scale Synthesis of Short Peptides via a Simplified ...
The synthesis started with the hydrochloride salt of the benzyl protected serine 15 and the desired pentapeptide sequence BocGRGDS 14 was obtained in over ...
[48]
Homo sapiens [gbpri]: 93487 - Codon usage table
Codon Usage Table with Amino Acids A style like CodonFrequency output ... Keyword example: ribosomal protein / MAP kinase. List of codon usage for each ...
[49]
Deterministic features of side-chain main-chain hydrogen bonds in ...
(a) The Ser/Thr residues show the greatest preference in forming intra-helical hydrogen bonds between the atoms O(gamma)(i) and O(i-4). More than half the ...
[50]
Serine and Threonine Residues Bend α-Helices in the χ 1 =g
There is a noticeable increase of the population of g− conformation if the α-helix is embedded in a hydrophobic environment like the cell membrane. Notably, Ser ...
[51]
Functional Versatility of AGY Serine Codons in Immunoglobulin ...
Nov 22, 2016 · AGY Ser codons are far more abundant in complementarity-determining regions (CDRs) of IgV-region genes than expected for random codon use.
[52]
Dissecting the catalytic triad of a serine protease - Nature
Apr 7, 1988 · We have examined the catalytic importance and interplay between residues within the catalytic triad by individual or multiple replacement with alanine(s).
[53]
Effect of selected Ser/Ala and Xaa/Pro mutations on the stability and ...
The single Ser/Ala mutations had a moderately stabilizing effect and concomitantly decreased catalytic efficiency. Introducing a second Ser/Ala mutation did not ...Missing: conservation flexible
[54]
Optimizing the stability of single-chain proteins by linker length and ...
May 26, 1998 · Analysis of folding and unfolding rates suggests that alanine acts largely by accelerating folding, whereas serine acts predominantly to slow ...
[55]
Molecular Basis for Ser/Thr Specificity in PKA Signaling - PMC - NIH
Jun 25, 2020 · The best-established synthetic PKA substrate is Kemptide, a heptapeptide (LRRASLG), and a canonical serine substrate derived from the porcine ...
[56]
The crucial role of protein phosphorylation in cell signaling and its ...
In particular, the phosphorylated residues of serine are 86.4%, followed by residues of threonine 11.8% whereas only 1.8% of tyrosine residues are ...
[57]
Phosphorylation of Ser 640 in Muscle Glycogen Synthase by DYRK ...
Glycogen synthase kinase-3 (GSK-3) phosphorylates four serine residues in the COOH terminus of glycogen synthase. Phosphorylation of one of these residues ...
[58]
d-Serine as the gatekeeper of NMDA receptor activity - Nature
Jun 9, 2020 · d-serine is now garnering attention as the primary NMDAR co-agonist in limbic brain regions implicated in neuropsychiatric disorders.
[59]
A quarter century of granzymes | Cell Death & Differentiation - Nature
Nov 4, 2011 · Grs are serine proteases, characterized by a His-Asp-Ser catalytic triad. In humans, there are 5 Grs (A, B, H, K, and M) while in mice ...
[60]
The three-dimensional structure of human granzyme B compared to ...
Granzyme B and the caspase family members are the only proteases that have been unequivocally established to be involved in cell death. Despite their distinct ...
[61]
The Development of Maillard Reaction, and Advanced Glycation ...
Advanced glycation end products (AGEs) are generated by nonenzymatic modifications of macromolecules (proteins, lipids, and nucleic acids) by saccharides ...
[62]
Advanced Glycation End Products | Circulation
Aug 8, 2006 · Advanced glycation end products (AGEs) are modifications of proteins or lipids that become nonenzymatically glycated and oxidized after contact ...
[63]
Serine synthesis controls mitochondrial biogenesis in macrophages
May 17, 2024 · This study reveals that a mechanism involving de novo serine synthesis orchestrates mitochondrial biogenesis via mitochondrial-to-nuclear communication.
[64]
De novo serine biosynthesis is protective in mitochondrial disease
May 27, 2025 · Our evidence indicates that de novo serine biosynthesis is essential to maintain mitochondrial respiration, redox balance, and cellular lipid homeostasis in ...Missing: 2024 | Show results with:2024
[65]
Insulin-regulated serine and lipid metabolism drive peripheral ...
Jan 25, 2023 · Here we demonstrate that aberrant serine homeostasis drives serine and glycine deficiencies in diabetic mice, which can be diagnosed with a serine tolerance ...
[66]
Supplementation with amino acid serine eases neuropathy in ...
Jan 25, 2023 · The team found that diabetic mice with low levels of two related amino acids, serine and glycine, are at higher risk for peripheral neuropathy.
[67]
Serine Deficiency Disorders - GeneReviews® - NCBI Bookshelf
Jun 22, 2023 · Proportion of Serine Deficiency Disorders ... Mild phenotypes of phosphoglycerate dehydrogenase deficiency by a novel mutation of PHGDH gene: Case ...Diagnosis · Clinical Characteristics · Differential Diagnosis · Genetic Counseling
[68]
Entry - #601815 - PHOSPHOGLYCERATE DEHYDROGENASE ...
Phosphoglycerate dehydrogenase deficiency (PHGDHD) is an autosomal recessive inborn error of L-serine biosynthesis that is characterized by congenital ...
[69]
Serine Metabolism in Health and Disease and as a Conditionally ...
May 9, 2022 · Glycine, produced from L-serine in reaction catalyzed by glycine hydroxymethyltransferase, is degraded by a group of enzymes called the glycine ...
[70]
D-Serine is a key determinant of glutamate toxicity in amyotrophic ...
Aug 30, 2007 · These results support the idea that Glu toxicity enhanced by D-Ser may play a pathological role not only in ALS mice models, but also in at ...
[71]
d-Amino acid oxidase controls motoneuron degeneration through d ...
Dec 27, 2011 · We previously reported that d-serine is increased in the spinal cord in both patients with sporadic/familial ALS and in a G93A-SOD1 mouse model ...
[72]
Oral Population Modeling of L-Serine in Humans - PubMed Central
May 13, 2021 · In sum, serine is a dietary component and even at fairly elevated dosing (∼30 g/day) showed rew reported adverse effects and those reported were ...
[73]
Serine metabolism: some tumors take the road less traveled - PMC
Cancer cells display a reprogramming of metabolism that facilitates growth but addicts them to key enzyme activities. Two studies in Nature and Nature Genetics ...
[74]
Increased serine synthesis provides an advantage for tumors arising ...
Plasma serine levels ranged from 92–314 μM (Figure 2D), values similar to the range of 53–262 μM reported for human plasma (Trabado et al., 2017).
[75]
Entry - #162400 - NEUROPATHY, HEREDITARY SENSORY ... - OMIM
A number sign (#) is used with this entry because hereditary sensory neuropathy type IA (HSAN1A) is caused by heterozygous mutation in the SPTLC1 gene (605712) ...
[76]
L-Serine Supplementation in Hereditary Sensory Neuropathy Type 1
The disease is caused by missense mutations in the SPTLC1 gene encoding a subunit of the enzyme serine palmitoyltransferase (SPT). In normal circumstances the ...