suktsinüülCoA

Succinyl-CoA is a crucial intermediate molecule in cellular metabolism, playing a central role in both the citric acid cycle and the synthesis of heme. It is formed from succinate, a four-carbon dicarboxylic acid, through the action of the enzyme succinate thiokinase, also known as succinyl-CoA synthetase. This reaction couples the cleavage of the thioester bond in succinyl-CoA with the phosphorylation of GDP to GTP, or ADP to ATP, depending on the specific organism and isoform of the enzyme.

In the citric acid cycle, succinyl-CoA is further metabolized to succinate, releasing Coenzyme A. This step is one of the two substrate-level phosphorylation reactions in the cycle, directly generating a high-energy phosphate bond. The breakdown of succinyl-CoA is essential for the continuous operation of the citric acid cycle, which generates reducing equivalents (NADH and FADH2) for ATP production through oxidative phosphorylation and also provides precursor molecules for various biosynthetic pathways.

Beyond its role in energy metabolism, succinyl-CoA is also a key precursor in the synthesis of porphyrins, which are essential components of heme. Heme is a vital molecule found in hemoglobin, myoglobin, and cytochromes, involved in oxygen transport and electron transfer, respectively. The pathway from succinyl-CoA to heme involves a series of enzymatic steps that ultimately lead to the formation of protoporphyrin IX, which is then chelated with iron to form heme.