|A service of the U.S. National Library of Medicine®|
On this page:
Reviewed July 2011
What is the official name of the MMAB gene?
The official name of this gene is “methylmalonic aciduria (cobalamin deficiency) cblB type.”
MMAB is the gene's official symbol. The MMAB gene is also known by other names, listed below.
Read more about gene names and symbols on the About page.
What is the normal function of the MMAB gene?
The MMAB gene provides instructions for making an enzyme that is involved in the formation of a compound called adenosylcobalamin (AdoCbl). AdoCbl, which is derived from vitamin B12 (also known as cobalamin), is necessary for the normal function of another enzyme known as methylmalonyl CoA mutase. This enzyme helps break down certain proteins, fats (lipids), and cholesterol.
The MMAB enzyme is active in mitochondria, which are specialized structures inside cells that serve as energy-producing centers. Once vitamin B12 has been transported into mitochondria, the MMAB enzyme converts a form of the vitamin called cob(I)alamin to AdoCbl. Studies suggest that this enzyme may also deliver AdoCbl to methylmalonyl CoA mutase.
How are changes in the MMAB gene related to health conditions?
Where is the MMAB gene located?
Cytogenetic Location: 12q24
Molecular Location on chromosome 12: base pairs 109,553,715 to 109,573,553
(Homo sapiens Annotation Release 107, GRCh38.p2) (
The MMAB gene is located on the long (q) arm of chromosome 12 at position 24.
More precisely, the MMAB gene is located from base pair 109,553,715 to base pair 109,573,553 on chromosome 12.
See How do geneticists indicate the location of a gene? in the Handbook.
Where can I find additional information about MMAB?
You and your healthcare professional may find the following resources about MMAB helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
What other names do people use for the MMAB gene or gene products?
See How are genetic conditions and genes named? in the Handbook.
Where can I find general information about genes?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding MMAB?
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (9 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.