Tricarboxylic acid cycle enzyme (TCA cycle enzyme)

Tricarboxylic acid cycle enzymes are a group of mitochondrial enzymes that catalyze the core biochemical reactions of the tricarboxylic acid (TCA) cycle, also known as the citric acid cycle or Krebs cycle, which is the central pathway for aerobic energy metabolism in almost all living cells[1][3][5][7][9]. These enzymes include citrate synthase, aconitase, isocitrate dehydrogenase (IDH1, IDH2, IDH3), α-ketoglutarate dehydrogenase, succinyl-CoA synthetase, succinate dehydrogenase, fumarase, and malate dehydrogenase, as well as related enzymes that regulate entry into the cycle, such as pyruvate dehydrogenase complex (PDH)[5][7]. Through the sequential oxidation of acetyl-CoA, TCA cycle enzymes generate NADH and FADH₂ for oxidative phosphorylation to produce ATP. The cycle also provides metabolic intermediates for biosynthetic pathways and redox regulation. Mutations or altered expression in TCA cycle enzymes are implicated in various diseases, notably cancer (mutant IDH1/2 in glioma and leukemia) and neurodegeneration (Alzheimer's disease, with alterations in PDHB, SUCLA2, MDH1)[2][3][4][6]. Several TCA enzymes and their mutants have become important drug targets, with inhibitors like ivosidenib and enasidenib used clinically in cancer therapy[2][3]. Because TCA enzymes are essential for normal cellular function, systemic inhibition carries notable metabolic risks. Note: “Tricarboxylic acid cycle enzymes” refers to a whole class of enzymes rather than a specific molecular entity. For structured data, each TCA enzyme should be mapped individually (e.g., Isocitrate dehydrogenase 1, Citrate synthase, etc.) rather than as a group, for specificity and practical use. Multiple enzymes are "therapeutic targets," especially mutant forms in disease, but grouping them as a single "target" may be too broad for most database schemas[2][3][4][5]. is_incorrect justification: The entry “Tricarboxylic acid cycle enzymes” is overly broad; it refers to a class of enzymes rather than a specific, actionable molecular target. Each TCA enzyme is a genetically and structurally distinct protein, often with unique clinical and pharmacological relevance. For precise, structured use, these should be separated into their canonical forms per enzyme (e.g., “Isocitrate dehydrogenase 1”, “Succinate dehydrogenase”, etc.)[5][7][2].

Other names

Citric acid cycle enzymeKrebs cycle enzymeSzent–Györgyi–Krebs cycle enzyme

Inhibition of mutant enzyme activity (e.g., mutant IDH1/2 inhibition prevents oncometabolite 2-hydroxyglutarate formation); Inhibition of key regulatory points (e.g., PDK inhibition increases PDH activity); Suppression of abnormal metabolite production; Modulation of metabolic flux through cycle