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Citrate synthase

Citrate synthase (CS; EC 2.3.3.1) is a pivotal enzyme in cellular metabolism, catalyzing the condensation of acetyl-coenzyme A (acetyl-CoA) and oxaloacetate to form citrate and coenzyme A, thereby initiating the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle or citric acid cycle.^[1]^[2]^[3] This reaction represents the first and rate-limiting step of the TCA cycle, linking carbohydrate, lipid, and protein catabolism to generate reducing equivalents (NADH and FADH₂) for ATP production via oxidative phosphorylation.^[1]^[3] Encoded by the nuclear gene CS on human chromosome 12q13.3, the enzyme is synthesized in the cytosol as a precursor with an N-terminal mitochondrial targeting sequence and imported into the mitochondrial matrix, where it functions as a homodimer (or higher-order oligomer in some species) with a molecular mass of approximately 100 kDa.^[2]^[3] The structure of citrate synthase exhibits an induced-fit mechanism, transitioning from an open conformation (accommodating substrates) to a closed form that excludes water and facilitates the reaction; in eukaryotes, each subunit features a large and small domain connected by a hinge, with the active site at their interface.^[1] Bacterial variants, such as from Escherichia coli, often form hexamers and include additional regulatory sites for NADH binding, which inhibits activity to prevent overproduction of cycle intermediates during high energy states.^[1] The enzyme's activity is tightly regulated by substrate availability, product inhibition (by citrate and succinyl-CoA), and post-translational modifications like lysine methylation, which can reduce catalytic efficiency.^[2]^[3] Beyond its core metabolic role, citrate synthase serves as a reliable biomarker for mitochondrial density and oxidative capacity in tissues, particularly skeletal muscle, due to its correlation with mitochondrial biogenesis.^[4] Dysregulation of citrate synthase has been implicated in metabolic disorders, including obesity, insulin resistance, and neurodegenerative conditions like Alzheimer's disease, where reduced activity may impair neuronal energy metabolism and acetylcholine synthesis.^[3] Across organisms, from bacteria to humans, the enzyme's conservation underscores its essentiality for aerobic respiration, with adaptations in thermophilic species featuring stabilizing disulfide bonds for function under extreme conditions.^[1]

Overview

Nomenclature and discovery

Citrate synthase is classified under the Enzyme Commission number EC 2.3.3.1, with the accepted name citrate (Si)-synthase.^[5] Its systematic name is acetyl-CoA:oxaloacetate C-acetyltransferase.^[5] The enzyme's activity was first identified in 1937 by Hans Adolf Krebs and William Arthur Johnson during their elucidation of the citric acid cycle, also known as the Krebs cycle or tricarboxylic acid cycle.^[6] Working at the University of Sheffield, they conducted experiments using minced pigeon breast muscle, which retained high oxidative capacity after tissue disruption, allowing observation of metabolic reactions in cell-free extracts.^[6] In these studies, addition of oxaloacetate to the muscle preparations, along with pyruvate or acetate, led to the formation of citrate, demonstrating the condensation reaction as the entry point for acetyl groups into the cycle.^[6] This discovery built on earlier observations by Albert Szent-Györgyi regarding citrate's role in oxidation but provided the mechanistic framework for the cycle's initial step.^[6] In humans, the enzyme is encoded by the CS gene, located on chromosome 12q13.3. The UniProt accession number for the human mitochondrial citrate synthase protein is O75390.^[7]

Biological role

Citrate synthase catalyzes the first committed step of the tricarboxylic acid (TCA) cycle, condensing acetyl-CoA derived from the catabolism of carbohydrates, fats, and proteins with oxaloacetate to form citrate.^[8] This reaction serves as the primary entry point for carbon units into the TCA cycle, integrating the oxidative breakdown of diverse macronutrients and funneling their energy content toward downstream mitochondrial processes.^[9] By initiating citrate formation, the enzyme bridges glycolytic pyruvate, beta-oxidized fatty acids, and amino acid degradation pathways, ensuring coordinated fuel utilization for cellular respiration.^[9] In eukaryotic cells, citrate synthase is localized to the mitochondrial matrix, where it plays a central role in energy homeostasis by enabling the TCA cycle to generate reducing equivalents such as NADH and FADH₂.^[10] These cofactors are subsequently oxidized in the electron transport chain, driving ATP synthesis via oxidative phosphorylation and supporting the majority of cellular energy demands.^[11] Disruption of citrate synthase activity impairs this linkage, leading to reduced mitochondrial ATP production and metabolic imbalances.^[11] The enzyme exerts significant flux control over the TCA cycle, functioning as a rate-limiting step under physiological conditions due to its position at the cycle's irreversible initiation.^[12] Its activity is primarily modulated by the availability of substrates, particularly acetyl-CoA supplied by pyruvate dehydrogenase, which responds to cellular energy status and nutrient influx./02:_Unit_II-_Bioenergetics_and_Metabolism/16:_The_Citric_Acid_Cycle/16.03:_Regulation_of_the_Citric_Acid_Cycle) This substrate-driven regulation allows citrate synthase to fine-tune cycle throughput, preventing overload and aligning metabolic flux with bioenergetic needs.^[13]

Molecular structure

Subunit architecture

Citrate synthase exhibits varied oligomeric states depending on the organism. In eukaryotes, such as porcine heart, the enzyme functions as a homodimer, with each subunit comprising approximately 466 amino acids and a molecular weight of about 50 kDa.^[14] In contrast, certain bacteria, including Escherichia coli, feature a hexameric form, reflecting structural adaptations in type II citrate synthases unique to Gram-negative species.^[15] These oligomeric assemblies are critical for stability and function, with the dimeric interface in eukaryotic variants burying a significant surface area through extensive intersubunit contacts. Each subunit folds into two distinct domains: a large domain and a small domain. The large domain (residues 55–410) adopts a Rossmann-like fold characterized by a central β-sheet flanked by α-helices, contributing to the overall scaffold and substrate positioning.^[16] The small domain (residues 1–54 and 411–437), consisting primarily of five α-helices with a small antiparallel β-sheet, enables conformational flexibility during catalysis.^[17] This domain organization is conserved across species, though subtle variations influence thermostability and allostery in bacterial hexamers.^[18] The quaternary interfaces, particularly in the eukaryotic dimer, are stabilized by a combination of hydrophobic contacts and hydrogen bonds, involving residues from both the large and small domains. These interactions form a buried hydrophobic core supplemented by polar bonds, ensuring structural integrity and cooperative behavior essential for enzymatic activity.^[19] Disruption of these interfaces, as observed in mutants, leads to loss of function, underscoring their biophysical importance. In hexameric bacterial forms, additional intersubunit contacts extend this network across the oligomer.^[15]

Active site features

The active site of citrate synthase resides in a cleft formed between the large and small domains of the enzyme, enabling precise substrate recognition and orientation. In the pig heart isoform, Asp375 and His320 play pivotal roles in oxaloacetate binding and enolization. His320 donates a hydrogen bond to the C2 carbonyl oxygen of oxaloacetate, polarizing the carbonyl group and stabilizing the developing negative charge during enol formation, while Asp375 positions the substrate and aids in proton abstraction from the incoming acetyl-CoA. These interactions ensure ordered binding, with oxaloacetate typically associating first to induce a conformational change that enhances affinity for the second substrate.^[20] For acetyl-CoA recognition, His274 and Asp375 coordinate the thioester carbonyl through hydrogen bonding, polarizing the carbonyl oxygen and facilitating nucleophilic attack by the enolized oxaloacetate. His274 specifically stabilizes the negative charge on the carbonyl during enolate formation, while Asp375 contributes to overall substrate alignment in the binding pocket. These residues create a complementary environment for the acetyl group's methyl and thioester moieties, promoting the condensation reaction.^[21]^[20] The citrate product is accommodated within a hydrophobic pocket lined by nonpolar residues such as Ile209 and Val285, which shield the central carbon chain from solvent. Arg421, contributed from the adjacent subunit in the dimer, forms a salt bridge with the C2-carboxyl group of citrate, enhancing product stability and release. Crystal structures, such as PDB entry 2CTS of the pig enzyme, illustrate this induced fit: substrate binding triggers an ~18° rotation of the small domain, closing the active site and excluding water to prevent premature hydrolysis.^[18]^[1]

Catalytic function

Reaction overview

Citrate synthase catalyzes the condensation of acetyl-coenzyme A (acetyl-CoA) with oxaloacetate in the presence of water to form citrate and coenzyme A (CoA-SH), marking the entry point for the two-carbon acetyl unit into the tricarboxylic acid (TCA) cycle. The stoichiometric equation for this reaction is:

\text{Acetyl-CoA} + \text{oxaloacetate} + \text{H}_2\text{O} \rightarrow \text{citrate} + \text{CoA-SH}

This transformation is highly exergonic under standard biochemical conditions (pH 7, 25°C), with a standard free energy change (ΔG°') of -32.2 kJ/mol, which strongly favors product formation and renders the reaction effectively irreversible in vivo.^[22] The equilibrium constant (K_eq) for the reaction, defined as K_eq = [\text{citrate}][\text{CoA-SH}] / [\text{acetyl-CoA}][\text{oxaloacetate}], is approximately 2.24 × 10^6 M^{-1} at pH 7.0 and 38°C in the presence of 1 mM free Mg^{2+}, reflecting the thermodynamic drive toward citrate production and the commitment of acetyl carbons to the TCA cycle.^[23] The irreversibility stems from the coupled hydrolysis of the high-energy thioester bond in acetyl-CoA, which releases sufficient energy to make reversal unfavorable under physiological concentrations, ensuring unidirectional flux through the cycle.^[22]

Kinetic parameters

Citrate synthase exhibits Michaelis-Menten kinetics for its substrates, oxaloacetate and acetyl-CoA, with the enzyme displaying a higher affinity for oxaloacetate. Representative values from mammalian sources include a K_m for oxaloacetate of approximately 2 μM and for acetyl-CoA of 16 μM, measured under conditions where the concentration of the other substrate is saturating. These low K_m values reflect the enzyme's efficiency in binding substrates at physiological concentrations, with variations across species and isoforms typically ranging from 3-10 μM for oxaloacetate and 10-50 μM for acetyl-CoA.^[24] The maximum velocity (V_{\max}) of citrate synthase is on the order of 100-200 s⁻¹ per active site (turnover number, k_{\text{cat}}), corresponding to a specific activity of around 140 units per mg protein in purified mammalian preparations. This high turnover rate underscores the enzyme's role as a pace-setting catalyst in the citric acid cycle, where the condensation of acetyl-CoA and oxaloacetate to form citryl-CoA represents the rate-limiting step under optimal conditions. Quantitative assessments from pig heart enzyme confirm a k_{\text{cat}} of approximately 283 s⁻¹, though values can vary with assay conditions and subunit oligomerization.^[25] The kinetic mechanism is an ordered bi-bi ternary complex type, in which oxaloacetate binds first to the open conformation of the enzyme, triggering a large-scale hinge-bending closure that creates the binding site for acetyl-CoA. This sequential binding ensures productive complex formation without release of intermediates until after the condensation and hydrolysis steps.^[26]^[27]

Reaction mechanism

Condensation step

The condensation step of the citrate synthase reaction involves the formation of a carbon-carbon bond between oxaloacetate and acetyl-CoA, producing the citryl-CoA intermediate. This process is initiated by the binding of oxaloacetate to the enzyme, which induces a conformational change that creates the binding site for acetyl-CoA.^[20] Enolization of acetyl-CoA occurs when the carboxylate side chain of Asp375 acts as a general base to abstract a proton from the methyl group of acetyl-CoA, generating a nucleophilic enolate intermediate. This deprotonation is facilitated by the protonated His274, which stabilizes the developing negative charge on the thioester carbonyl oxygen through hydrogen bonding, effectively forming part of an oxyanion hole along with a nearby water molecule.^[20]^[28] The enolate then performs a nucleophilic attack on the electrophilic carbonyl carbon of oxaloacetate. This attack is promoted by His320, which donates a hydrogen bond to the carbonyl oxygen of oxaloacetate, polarizing it and enhancing its reactivity. The resulting tetrahedral intermediate collapses to form the C-C bond, yielding the thioester-linked citryl-CoA.^[20]^[29] During this nucleophilic addition, the transition state featuring the oxyanion from the oxaloacetate carbonyl is stabilized by an oxyanion hole composed of the backbone amide hydrogens from Gly326 and Gly330, which provide hydrogen bonds to mitigate the negative charge buildup. This stabilization lowers the activation energy for bond formation.^[28]^[30]

Hydrolysis step

In the hydrolysis step of the citrate synthase reaction, a water molecule is activated by the imidazole group of His274, which serves as a general base to abstract a proton from the water, generating a nucleophilic hydroxide that attacks the carbonyl carbon of the citryl-CoA thioester bond. This nucleophilic attack forms a tetrahedral oxyanion intermediate, in which the negative charge on the oxygen is stabilized by hydrogen bonding from His274 and nearby residues such as Asp375.^[20] The tetrahedral intermediate subsequently collapses, reforming the planar carbonyl group of citrate and expelling the coenzyme A (CoA) as a thiolate anion. The side chain of Arg401 plays a key role in facilitating the departure of the CoA thiolate by forming electrostatic interactions that stabilize and direct the leaving group away from the active site.^[31] This hydrolysis does not require any additional cofactors beyond the substrates and relies entirely on the enzyme's active site architecture for catalysis. The reaction exhibits pH dependence, with optimal enzymatic activity occurring between pH 7.5 and 8.0, reflecting the ionization states of key catalytic residues like His274.^[32]

Regulation

Allosteric control

Substrate binding induces a critical conformational change in citrate synthase, transitioning the enzyme from an open to a closed state that facilitates catalysis. Oxaloacetate binds first to the active site, triggering a rotation of the small domain relative to the large domain by approximately 18 degrees, which creates the binding site for acetyl-CoA and shields the intermediates from solvent. This induced-fit mechanism is essential for efficient condensation and is influenced by allosteric effectors that stabilize either the open or closed form.^[33] Negative allosteric regulation occurs through binding of NADH and succinyl-CoA to a dedicated regulatory site, which stabilizes the open conformation and reduces the maximum velocity (V_max) of the enzyme by 50-90% at physiological concentrations. This feedback inhibition prevents overproduction of TCA cycle intermediates when reducing equivalents and downstream products accumulate, as observed in prokaryotic models like chickpea bacteroids where 80 μM NADH inhibits activity by 50% and 200 μM by over 90%. In mammalian mitochondria, similar inhibition by NADH and succinyl-CoA (competitive with acetyl-CoA) fine-tunes cycle flux to match oxidative capacity.^[34]^[35] Additionally, ATP exerts competitive inhibition with respect to acetyl-CoA, reflecting high energy status and reducing substrate access to the active site. This mechanism integrates adenine nucleotide levels directly into cycle regulation, with Ki values indicating sensitivity at physiological ATP concentrations in rat liver mitochondria.^[36]

Inhibitory mechanisms

Citrate, the product of the citrate synthase reaction, serves as a feedback inhibitor to regulate the enzyme's activity and prevent overproduction in the tricarboxylic acid (TCA) cycle. This inhibition is competitive with respect to the substrate oxaloacetate, with a reported K_i value of 1.6 mM for mammalian citrate synthase (e.g., pig heart).^[37] Such product inhibition is a common regulatory feature across species, including mammalian citrate synthases, where it similarly competes at the oxaloacetate binding site to modulate flux through the cycle. Post-translational phosphorylation represents a covalent modification that downregulates citrate synthase in certain isoforms, particularly in response to cellular signaling. In the yeast Saccharomyces cerevisiae, phosphorylation at the serine residue Ser462 by mitochondrial kinases disrupts homodimer formation, which is essential for catalytic activity, leading to complete abolition of enzyme function.^[38] This mechanism allows for rapid, reversible control of TCA cycle entry under varying metabolic conditions, though the extent of activity reduction can vary by isoform and organism. Additionally, post-translational modifications such as lysine methylation can reduce catalytic efficiency.^[3] Fluorocitrate, a structural analog of citrate produced via "lethal synthesis" from fluoroacetate, functions as a potent inhibitor of citrate synthase and is employed in metabolic studies to dissect TCA cycle dynamics. It exhibits very low K_i values, indicating tight binding, and has been noted for its ability to interfere with enzyme function through analog-specific interactions at the active site. This compound's use highlights external factors that mimic product inhibition but with prolonged effects, aiding research on cycle regulation independent of allosteric effectors.

Isoforms and evolution

Prokaryotic and eukaryotic variants

Citrate synthase (CS) enzymes exhibit structural and functional variations between prokaryotes and eukaryotes, reflecting adaptations to distinct cellular environments and metabolic demands. In prokaryotes, particularly Gram-negative bacteria like Escherichia coli, CS is classified as a type II enzyme and assembles into a hexameric structure composed of three identical dimer units arranged around a central threefold axis. This quaternary organization facilitates allosteric regulation, with NADH binding at interfaces between dimer units to inhibit activity under high-energy conditions. The active site in bacterial CS requires significant structural rearrangements, including shifts in key residues like His264, to accommodate substrates, distinguishing it from the more rigid binding in eukaryotic forms. In contrast, eukaryotic CS belongs to the type I family and functions as a homodimer, with each subunit contributing residues to the shared active site cleft formed between the small N-terminal and large C-terminal domains. This dimeric architecture is conserved across animals, fungi, and plants, enabling reversible conformational changes from an open to a closed state upon substrate binding. Eukaryotic CS is localized to the mitochondrial matrix, where the precursor protein includes an N-terminal mitochondrial targeting sequence (MTS) of approximately 25-30 residues that is cleaved by matrix processing peptidase upon import; for example, the human CS MTS spans residues 1-27.^[39] Unlike many bacterial variants, eukaryotic CS generally lacks strong allosteric inhibition by NADH, relying instead on substrate availability and product inhibition for control, which contributes to its role as a relatively unregulated entry point into the tricarboxylic acid cycle. Plants display additional isoform diversity, with both mitochondrial and cytosolic CS variants encoded by nuclear genes. The mitochondrial isoform mirrors eukaryotic type I CS in structure and function, participating in the tricarboxylic acid cycle to generate energy and biosynthetic precursors. The cytosolic isoform produces citrate in the cytoplasm, which can be cleaved by ATP-citrate lyase to yield acetyl-CoA for de novo fatty acid biosynthesis, particularly in developing seeds and during lipid accumulation under nutrient stress. This dual localization allows plants to coordinate mitochondrial respiration with cytosolic lipid metabolism, with expression of the cytosolic form upregulated in response to high carbon availability. Sequence conservation across these variants underscores a common catalytic core, though prokaryotic and eukaryotic forms diverged early in evolution.

Evolutionary conservation

Citrate synthase is a highly conserved enzyme found ubiquitously in aerobic organisms, where it initiates the tricarboxylic acid (TCA) cycle essential for oxidative energy production, but it is absent in strict anaerobes that employ alternative fermentative or reductive pathways.^[40]^[41] The enzyme's origins date back to the early stages of life on Earth, approximately 3.5 billion years ago, aligning with the emergence of primitive metabolic networks that later adapted to rising atmospheric oxygen levels around 2.4 billion years ago during the Great Oxidation Event, enabling the full aerobic TCA cycle.^[42]^[43] Phylogenetic analyses trace citrate synthase to eubacterial ancestors, with eukaryotic mitochondrial variants deriving from α-proteobacterial endosymbionts, underscoring its fundamental role in cellular respiration across domains of life.^[42] Sequence comparisons demonstrate remarkable evolutionary conservation, with 40-50% amino acid identity between bacterial citrate synthases, such as that from Escherichia coli, and the human mitochondrial enzyme, reflecting shared structural and functional core despite billions of years of divergence.^[44] This homology extends to key active site residues, including the conserved catalytic triad of histidine-aspartate-histidine (His274, Asp375, His320 in porcine numbering), which facilitates substrate binding, enolization, and condensation through acid-base catalysis—a feature invariant across prokaryotes and eukaryotes.^[29]^[16] Such preservation highlights the enzyme's critical positioning in metabolism, where even minor variations could disrupt energy homeostasis. Gene duplication events have contributed to isoform diversification, allowing compartmentalization and specialized functions in certain lineages; for instance, fungi exhibit mitochondrial (Cit1p) and peroxisomal (Cit2p) isoforms arising from duplication, while plants possess glyoxysomal variants integrated into the glyoxylate cycle.^[42] In mammals, a single nuclear gene encodes the primary mitochondrial citrate synthase, though post-translational modifications and regulatory mechanisms mimic isoform-like adaptations to metabolic demands.^[45] These evolutionary adaptations underscore citrate synthase's versatility while maintaining its core catalytic integrity across aerobic life forms.^[42]

Clinical and pathological aspects

Associated disorders

Mutations in the SLC25A1 gene, which encodes the mitochondrial citrate carrier responsible for exporting citrate produced by citrate synthase, cause a rare neurometabolic disorder known as combined D-2- and L-2-hydroxyglutaric aciduria (D/L-2-HGA). These biallelic loss-of-function mutations impair citrate export from the mitochondrial matrix to the cytosol, disrupting the flux through the tricarboxylic acid (TCA) cycle and leading to accumulation of hydroxyglutaric acids, lactic acidosis, progressive encephalopathy, epilepsy, hypotonia, and developmental delay. Reported pathogenic variants include p.Arg206His and p.Gln94Argfs*14, with affected individuals exhibiting severe neurological symptoms from infancy.^[46] In East Asian populations, citrin deficiency due to biallelic mutations in SLC25A13, the gene encoding the mitochondrial aspartate-glutamate carrier 2 (citrin), manifests as adult-onset type II citrullinemia (CTLN2). This disorder indirectly impacts citrate synthase flux by disrupting the malate-aspartate shuttle, which alters cytosolic NADH/NAD+ ratios and leads to deviations in circulating TCA cycle metabolites, including reduced citrate levels and impaired hepatic energy metabolism. Clinical features include hyperammonemia, neuropsychiatric symptoms, fatigue, and aversion to carbohydrates, with the condition being highly prevalent in Japan and other East Asian countries due to founder mutations like IVS16ins3kb and R180X.^[47]^[48] Upregulation of citrate synthase expression supports metabolic reprogramming in various cancers, including glioblastoma, where elevated TCA cycle activity facilitates biosynthesis of lipids and nucleotides essential for tumor proliferation. In preclinical models, knockdown of citrate synthase significantly reduces tumor growth; for instance, in prostate cancer xenografts, CS silencing significantly inhibited tumor growth compared to controls over 5 weeks, accompanied by decreased proliferation and invasion markers. Similar effects have been observed in ovarian and breast cancer cells, underscoring CS as a potential oncogenic driver.^[49]^[50]

Therapeutic implications

Citrate synthase (CS) serves as a promising therapeutic target in cancer therapy, particularly for hypoxic tumors that rely on TCA cycle flux to sustain proliferation under oxygen-limited conditions. Natural polyphenolic compounds, such as ellagic acid, act as inhibitors of mitochondrial respiration, thereby reducing TCA cycle activity and impairing tumor growth. In lung cancer cell lines and xenograft models, ellagic acid decreases oxygen consumption rates, inner mitochondrial membrane potential, and ATP production while suppressing hypoxia-inducible factor 1-alpha (HIF-1α) expression, leading to inhibited cell proliferation and reduced tumor volume without significant toxicity to normal tissues.^[51] These effects highlight the potential of ellagic acid derivatives to disrupt metabolic reprogramming in hypoxic environments, offering a basis for developing targeted anti-cancer agents that limit TCA-dependent bioenergetics in solid tumors.^[51] Gene therapy strategies employing adeno-associated virus (AAV) vectors show preclinical promise for mitochondrial disorders involving TCA cycle impairments. AAV-mediated delivery of therapeutic genes has successfully ameliorated phenotypes in related mitochondrial diseases by enhancing mitochondrial enzyme activities, including those in the TCA cycle, through targeted expression in affected tissues like muscle and brain. Although direct applications to citrate synthase-related dysfunctions remain in early exploration, AAV vectors—such as AAV9 serotypes—have demonstrated safe, long-term transgene expression and partial phenotypic rescue in models of TCA cycle disruptions, suggesting feasibility for elevating mitochondrial CS levels to normalize citrate production and metabolic homeostasis. In neurodegeneration, particularly Alzheimer's disease (AD), diminished CS activity correlates with reduced citrate levels, exacerbating amyloid-beta (Aβ) toxicity by impairing cellular energy production and acetylcholine synthesis. Experimental evidence indicates that elevating citrate inhibits Aβ aggregation in vitro and confers neuroprotection against Aβ-induced toxicity in neuronal cell models, mitigating oxidative stress and apoptosis. Consequently, CS overexpression in AD models has been shown to ameliorate Aβ toxicity via enhanced citrate-mediated mechanisms, promoting mitochondrial bioenergetics and synaptic function as a potential neuroprotective strategy.^[52]^[52]

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Aberrant Expression of Citrate Synthase is Linked to Disease ...
Jul 22, 2020 · Citrate synthase (CS) is a rate-limiting enzyme in the citrate cycle and is capable of catalyzing oxaloacetate and acetyl-CoA to citrate.
[45]
Citrate Synthase Expression Affects Tumor Phenotype and Drug ...
Increased CS has been observed in pancreatic cancer. In this study, we found higher CS expression in malignant ovarian tumors and ovarian cancer cell lines ...
[46]
https://pubmed.ncbi.nlm.nih.gov/29031613/
[47]
https://www.ncbi.nlm.nih.gov/books/NBK1181/