Succinyl-CoA

Succinyl-CoA is a high-energy thioester formed in metabolism and a citric-acid-cycle intermediate. It supplies carbon for heme synthesis, ketone-body metabolism, and other pathways.

Succinyl-CoA synthetase: An enzyme that reversibly converts succinyl-CoA and phosphate into succinate and a nucleoside triphosphate. It couples succinyl-CoA breakdown to substrate-level phosphorylation in the cycle.
Coenzyme A: A cofactor that carries acyl groups through metabolism using a reactive terminal thiol. Its thiol forms the thioester bond that distinguishes succinyl-CoA from succinate.
Heme biosynthesis: The pathway that builds heme, an iron-containing cofactor used in oxygen transport and electron transfer. In animals, succinyl-CoA contributes carbon to the first committed precursor of heme.
Methylmalonyl-CoA: A CoA-linked three-carbon intermediate that is rearranged into succinyl-CoA. It provides a distinct route into the cycle, especially during odd-chain fatty-acid and amino-acid breakdown.
Substrate-level phosphorylation: The direct formation of ATP or another nucleoside triphosphate by transferring a phosphate group from a metabolic intermediate. The succinyl-CoA synthetase reaction makes GTP or ATP without the respiratory chain.
Succinic acid: A four-carbon dicarboxylic acid whose ionized form is succinate. Succinyl-CoA carries this carbon skeleton in an activated, coenzyme-linked form.
Delta-aminolevulinic acid: A small amino ketone that is the first committed precursor in heme biosynthesis. Glycine and succinyl-CoA combine to produce it in animal mitochondria.
Methylmalonyl-CoA mutase: A vitamin B12-dependent enzyme that rearranges methylmalonyl-CoA into succinyl-CoA. It makes succinyl-CoA from propionyl-CoA-derived carbon rather than from alpha-ketoglutarate.
Succinate: A four-carbon dicarboxylate produced from succinyl-CoA in the citric acid cycle. It is the product formed when the thioester bond is cleaved.
Alpha-ketoglutarate: A five-carbon keto acid in the citric acid cycle and a precursor to succinyl-CoA. Its oxidative decarboxylation is a major route for making succinyl-CoA.

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