Methylmalonic acid is a dicarboxylic acid

Dicarboxylic acid

Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group...

 that is a C-methylated

Methylation

In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...

 derivative of malonate

Malonate

The malonate or propanedioate ion is CH222− . Malonate compounds include salts and esters of malonic acid, such as*diethyl malonate, 2,*dimethyl malonate, 2,...

.

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, methylmalonyl-CoA

Methylmalonyl-CoA

Methylmalonyl-CoA is the coenzyme A linked form of methylmalonic acid. Methylmalonyl-CoA is formed from propionyl-CoA by propionyl-CoA carboxylase by help of biotin . It is converted into succinyl-CoA by methylmalonyl-CoA mutase, in a reaction that requires vitamin B12 as a cofactor...

, 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 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...

.

Pathology

Increased methylmalonic acid levels may indicate a 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...

 deficiency. However, it is sensitive without being specific. MMA is elevated in 90-98% of patients with B₁₂ deficiency. This test may be overly sensitive, as 20-25% of patients over the age of 70 have elevated levels of MMA, but 25-33% of them do not have B₁₂ deficiency. For this reason, MMA test is not routinely recommended in the elderly.

An excess is associated with methylmalonic acidemia

Methylmalonic acidemia

Methylmalonic acidemia , also called methylmalonic aciduria, is an autosomal recessive metabolic disorder. It is a classical type of organic acidemia....

.

MMA concentrations in blood are measured by Gas chromatographic

Gas-liquid chromatography

Gas chromatography , is a common type of chromatography used in analytical chemistry for separating and analysing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture...

 Mass spectrometry

Mass spectrometry

Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...

and the expected values of MMA in healthy people are between 73-271 nmol/L.