Methylmalonyl-CoA is the coenzyme A

Coenzyme A

Coenzyme A is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All sequenced genomes encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it as a substrate...

 linked form of methylmalonic acid

Methylmalonic acid

Methylmalonic acid is a dicarboxylic acid that is a C-methylated derivative of malonate.The coenzyme A linked form of methylmalonic acid, methylmalonyl-CoA, is converted into succinyl-CoA by methylmalonyl-CoA mutase, in a reaction that requires vitamin B12 as a cofactor...

. Methylmalonyl-CoA is formed from propionyl-CoA

Propionyl-CoA

Propionyl-CoA is a coenzyme A derivative of propionic acid.-Production:There are several different ways in which it is formed:* It is formed as a product of beta-oxidation of odd-chain fatty acids....

 by propionyl-CoA carboxylase

Propionyl-CoA carboxylase

Propionyl-CoA carboxylase catalyses the carboxylation reaction of propionyl CoA in the mitochondrial matrix. The enzyme is biotin dependent. The product of the reaction is -methylmalonyl CoA. Propionyl CoA is the end product of metabolism of odd-chain fatty acids, and is also a metabolite of most...

 by help of biotin

Biotin

Biotin, also known as Vitamin H or Coenzyme R, is a water-soluble B-complex vitamin discovered by Bateman in 1916. It is composed of a ureido ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring...

 (vitamin B₇). It is converted into succinyl-CoA

Succinyl-CoA

Succinyl-Coenzyme A, 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 α-Ketoglutarate by α-ketoglutarate dehydrogenase through decarboxylation...

 by methylmalonyl-CoA mutase

Methylmalonyl-CoA mutase

Methylmalonyl Coenzyme A mutase, also known as MCM is an enzyme that catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA and it is involved in key metabolic pathways...

, in a reaction that requires vitamin B₁₂

Vitamin B12

Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...

 as a cofactor. In this way, it enters the Krebs cycle, and is thus part of one of the anaplerotic reactions

Anaplerotic reactions

Anaplerotic reactions are those that form intermediates of a metabolic pathway. Examples of such are found in the Tricarboxylic acid Cycle...

. The following diagram demonstrates the aforementioned reactions:

Propionyl CoA → Methylmalonyl CoA → Succinyl CoA