Succinyl-CoA synthetase functions in the citric acid cycle (TCA), coupling the hydrolysis of succinyl-CoA to the synthesis of ATP and thus represents the only step of substrate-level phosphorylation in the TCA. The alpha subunit of the enzyme binds the substrates coenzyme A and phosphate, while succinate binding and nucleotide specificity is provided by the beta subunit. CoA + GTP + succinate = GDP + phosphate + succinyl-CoA ATP + CoA + succinate = ADP + phosphate + succinyl-CoA Carbohydrate metabolism; tricarboxylic acid cycle; succinate from succinyl-CoA (ligase route): step 1/1. Heterodimer of an alpha and a beta subunit. Belongs to the succinate/malate CoA ligase alpha subunit family.