Succinyl-CoA

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Succinyl -coenzyme A (short: succinyl-CoA ) is a thioester of the succinic acid with coenzyme A. In biochemistry therefore the anion is referred to. Succinyl -CoA occurs as an intermediate in various metabolic processes.

Importance in the Citric Acid Cycle

Succinyl -CoA is produced in the citric acid cycle from α -ketoglutarate by oxidative decarboxylation and formation of a thioester with coenzyme A. The multi-step reaction is catalyzed by the α -ketoglutarate dehydrogenase complex. Per molecule of unreacted α -ketoglutarate, a molecule of CO2 and NADH are formed each. In the further course of the citric acid cycle succinyl -CoA is cleaved by the succinyl- CoA synthetase in succinate and coenzyme A. In addition, a molecule of high-energy phosphate compound, which is either GTP or ATP is produced.

Further reactions

• Succinyl -CoA is also formed from propionyl CoA, with the participation of the enzyme propionyl -CoA carboxylase, methylmalonyl CoA epimerase and methylmalonyl- CoA mutase. This reaction is one of the anaplerotic reactions. Thus, succinyl-CoA is the point of entry into the citric acid cycle for parts of the carbon skeletons of the amino acids isoleucine, valine, methionine and threonine.

• Succinyl -CoA is one of the starting materials in the synthesis of porphyrins and is withdrawn for the Citric Acid Cycle ( kataplerotische reaction). Here, succinyl -CoA reacts with glycine to δ - aminolevulinate. The reaction is catalyzed by the δ - aminolevulinate synthase. Succinyl -CoA is thus a raw material for the structure of the heme complex which is inter alia contained in red blood pigment hemoglobin.

• The recovery of the ketone body acetoacetate is introduced by the succinyl-CoA coenzyme A to acetoacetate gives whereby acetoacetyl -CoA and succinate occur. The exchange is catalyzed by 3 -keto acid -CoA transferase ( SCOT ).

• There are indications that succinyl-CoA is also the end product of the β - oxidation of dicarboxylic acids, in the peroxisomes of the liver and kidney. Here, succinyl- CoA is cleaved by the succinyl -CoA thioesterase ( ACOT4 ) into succinate and CoA. Dicarboxylic acids produced by ω - oxidation of fatty acids.