Methylmalonic acid (MMA) (conjugate base methylmalonate) is a dicarboxylic acid that is a C-methylated derivative of malonate.

Methylmalonic acid
Methylmalonic acid.svg
IUPAC name
2-Methylpropanedioic acid
Other names
Methylmalonic acid
3D model (JSmol)
ECHA InfoCard 100.007.473
EC Number
  • 208-219-5
MeSH Methylmalonic+acid
Molar mass 118.088 g/mol
Density 1.455 g/cm−3
Melting point 134 °C (273 °F; 407 K)
Acidity (pKa) pKa1 = 3,07[1]
pKa2 = 5,76[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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


Increased methylmalonic acid levels may indicate a vitamin B12 deficiency. However, it is sensitive (those with the disease almost always test positive) but not specific (those that do not have the disease do not always test negative).[2] MMA is elevated in 90–98% of patients with B12 deficiency. It has lower specificity 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.[3]

An excess is associated with methylmalonic acidemia.

MMA concentrations in blood are measured by gas chromatographic mass spectrometry or LC-MS and the expected values of MMA in healthy people are between 73–271 nmol/l.[4][5]

See alsoEdit


  1. ^ a b "Dissociation Constants Of Organic Acids And Bases".
  2. ^ "Sensitivity and Specificity".
  3. ^ "B12 Deficiiency and Dizziness".
  4. ^ Isber, Sonia (2007). "The role of poor nutritional status and hyperhomocysteinemia in complicated pregnancy in Syria" (PDF). doi:10.22028/D291-20838. Cite journal requires |journal= (help)
  5. ^ "Methylmalonic Acid, Serum or Plasma (Vitamin B12 Status)".

Further readingEdit