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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed October 2008

What is the official name of the MCCC2 gene?

The official name of this gene is “methylcrotonoyl-CoA carboxylase 2.”

MCCC2 is the gene's official symbol. The MCCC2 gene is also known by other names, listed below.

What is the normal function of the MCCC2 gene?

The MCCC2 gene provides instructions for making one part (the beta subunit) of an enzyme called 3-methylcrotonoyl-CoA carboxylase or 3-MCC. Beta subunits join with larger alpha subunits made from the MCCC1 gene; six of these pairings together form a functioning enzyme.

The 3-MCC enzyme is found in mitochondria, which are the energy-producing centers inside cells. This enzyme plays a critical role in breaking down proteins obtained from the diet. Specifically, it is responsible for the fourth step in the breakdown of leucine, an amino acid that is a building block of many proteins. This step converts a molecule called 3-methylcrotonyl-CoA to a molecule called 3-methylglutaconyl-CoA. Additional chemical reactions convert 3-methylglutaconyl-CoA into molecules that are later used for energy.

How are changes in the MCCC2 gene related to health conditions?

3-methylcrotonyl-CoA carboxylase deficiency - caused by mutations in the MCCC2 gene

More than 40 mutations in the MCCC2 gene have been identified in people with 3-methylcrotonyl-CoA carboxylase deficiency (also known as 3-MCC deficiency). Most of these mutations change single amino acids in 3-MCC, which severely reduces the activity of the enzyme. Other mutations prevent the production of any functional enzyme. As a result, leucine cannot be broken down properly, and byproducts of leucine processing build up to toxic levels in the body. These toxic substances can damage the brain, causing the characteristic signs and symptoms of 3-MCC deficiency.

Where is the MCCC2 gene located?

Cytogenetic Location: 5q12-q13

Molecular Location on chromosome 5: base pairs 71,587,288 to 71,658,706

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The MCCC2 gene is located on the long (q) arm of chromosome 5 between positions 12 and 13.

The MCCC2 gene is located on the long (q) arm of chromosome 5 between positions 12 and 13.

More precisely, the MCCC2 gene is located from base pair 71,587,288 to base pair 71,658,706 on chromosome 5.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about MCCC2?

You and your healthcare professional may find the following resources about MCCC2 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 MCCC2 gene or gene products?

  • 3-methylcrotonyl-CoA carboxylase non-biotin-containing subunit
  • MCCase subunit beta
  • MCCB
  • methylcrotonoyl-CoA carboxylase 2 (beta)
  • non-biotin containing subunit of 3-methylcrotonyl-CoA carboxylase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding MCCC2?

acids ; amino acid ; biotin ; breakdown ; carboxylase ; CoA ; deficiency ; enzyme ; gene ; leucine ; mitochondria ; molecule ; subunit ; toxic

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Baumgartner MR, Almashanu S, Suormala T, Obie C, Cole RN, Packman S, Baumgartner ER, Valle D. The molecular basis of human 3-methylcrotonyl-CoA carboxylase deficiency. J Clin Invest. 2001 Feb;107(4):495-504. (
  • Dantas MF, Suormala T, Randolph A, Coelho D, Fowler B, Valle D, Baumgartner MR. 3-Methylcrotonyl-CoA carboxylase deficiency: mutation analysis in 28 probands, 9 symptomatic and 19 detected by newborn screening. Hum Mutat. 2005 Aug;26(2):164. (
  • Desviat LR, Pérez-Cerdá C, Pérez B, Esparza-Gordillo J, Rodríguez-Pombo P, Peñalva MA, Rodríguez De Córdoba S, Ugarte M. Functional analysis of MCCA and MCCB mutations causing methylcrotonylglycinuria. Mol Genet Metab. 2003 Nov;80(3):315-20. (
  • Gallardo ME, Desviat LR, Rodríguez JM, Esparza-Gordillo J, Pérez-Cerdá C, Pérez B, Rodríguez-Pombo P, Criado O, Sanz R, Morton DH, Gibson KM, Le TP, Ribes A, de Córdoba SR, Ugarte M, Peñalva MA. The molecular basis of 3-methylcrotonylglycinuria, a disorder of leucine catabolism. Am J Hum Genet. 2001 Feb;68(2):334-46. Epub 2001 Jan 17. (
  • Holzinger A, Röschinger W, Lagler F, Mayerhofer PU, Lichtner P, Kattenfeld T, Thuy LP, Nyhan WL, Koch HG, Muntau AC, Roscher AA. Cloning of the human MCCA and MCCB genes and mutations therein reveal the molecular cause of 3-methylcrotonyl-CoA: carboxylase deficiency. Hum Mol Genet. 2001 Jun 1;10(12):1299-306. (
  • NCBI Gene (
  • Stadler SC, Polanetz R, Maier EM, Heidenreich SC, Niederer B, Mayerhofer PU, Lagler F, Koch HG, Santer R, Fletcher JM, Ranieri E, Das AM, Spiekerkötter U, Schwab KO, Pötzsch S, Marquardt I, Hennermann JB, Knerr I, Mercimek-Mahmutoglu S, Kohlschmidt N, Liebl B, Fingerhut R, Olgemöller B, Muntau AC, Roscher AA, Röschinger W. Newborn screening for 3-methylcrotonyl-CoA carboxylase deficiency: population heterogeneity of MCCA and MCCB mutations and impact on risk assessment. Hum Mutat. 2006 Aug;27(8):748-59. (


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.

Reviewed: October 2008
Published: February 8, 2016