Succinyl-CoA

Succinyl-Coenzyme A, generally abbreviated as Succinyl-CoA or SucCoA is a combination of succinic acid and coenzyme A.

Source
It is an important intermediate in the citric acid cycle, where it is synthesized from &alpha;-Ketoglutarate by &alpha;-ketoglutarate dehydrogenase through decarboxylation. During the process, coenzyme A is added.

It is also synthesized from propionyl CoA, the odd numbered fatty acid which cannot undergo beta-oxidation. Propionyl-CoA is carboxylated to D-methylmalonyl-CoA, isomerized to L-methylmalonyl-CoA, and rearranged to yield succinyl-CoA via a vitamin B12-dependent enzyme. Succinyl-CoA is an intermediate of the citric acid cycle and can be readily incorporated there.

Fate
It is converted into succinate through the hydrolytic release of coenzyme A by succinyl-CoA synthetase (succinate thiokinase).

Another fate of succinyl-CoA is porphyrin synthesis, where succinyl-CoA and glycine are combined by ALA synthase to form &delta;-aminolevulinic acid (dALA).

Formation
Succinyl CoA can be formed from methylmalonyl CoA through the utilization of deoxyadenosyl-B12 (deoxyadenosylcobalamin) by methylmalonyl CoA Mutase. This reaction, which requires vitamin B12 to occur, is important in the catabolism of some branched-chain amino acids as well as odd-chain fatty acids.