succinatecoenzyme

Succinatecoenzyme, also known as succinyl-CoA, is a vital intermediate molecule in cellular metabolism. It plays a crucial role in both the citric acid cycle, also known as the Krebs cycle, and in the synthesis of heme. Succinyl-CoA is formed from succinate, a four-carbon dicarboxylic acid, by the enzyme succinyl-CoA synthetase. This reaction couples the cleavage of a high-energy thioester bond in succinyl-CoA with the phosphorylation of guanosine diphosphate (GDP) to guanosine triphosphate (GTP) or adenosine diphosphate (ADP) to adenosine triphosphate (ATP), depending on the specific organism.

The primary function of succinyl-CoA is as a substrate in the citric acid cycle. In this cycle, succinyl-CoA is converted to succinate, releasing coenzyme A. This step is important for generating energy in the form of GTP or ATP. Beyond the citric acid cycle, succinyl-CoA is a key precursor for the synthesis of porphyrins, which are essential components of heme, chlorophyll, and cobalamin (vitamin B12). The conversion of succinyl-CoA to $\delta$-aminolevulinic acid is the first committed step in the heme biosynthetic pathway. Disorders affecting succinyl-CoA metabolism can lead to various metabolic diseases.