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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 MCCC1 gene?

The official name of this gene is “methylcrotonoyl-CoA carboxylase 1.”

MCCC1 is the gene's official symbol. The MCCC1 gene is also known by other names, listed below.

What is the normal function of the MCCC1 gene?

The MCCC1 gene provides instructions for making one part (the alpha subunit) of an enzyme called 3-methylcrotonoyl-CoA carboxylase or 3-MCC. Alpha subunits join with smaller beta subunits made from the MCCC2 gene; six of these pairings together form a functioning enzyme. The alpha subunit also includes a region for binding to the B vitamin biotin, which is required for the enzyme's function.

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 MCCC1 gene related to health conditions?

3-methylcrotonyl-CoA carboxylase deficiency - caused by mutations in the MCCC1 gene

At least 30 mutations in the MCCC1 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, but a few mutations lead to the production of an abnormally short version of the enzyme. Mutations in the MCCC1 gene severely reduce or eliminate the activity of 3-MCC. 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 MCCC1 gene located?

Cytogenetic Location: 3q27

Molecular Location on chromosome 3: base pairs 183,015,218 to 183,099,587

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

The MCCC1 gene is located on the long (q) arm of chromosome 3 at position 27.

The MCCC1 gene is located on the long (q) arm of chromosome 3 at position 27.

More precisely, the MCCC1 gene is located from base pair 183,015,218 to base pair 183,099,587 on chromosome 3.

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

Where can I find additional information about MCCC1?

You and your healthcare professional may find the following resources about MCCC1 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 MCCC1 gene or gene products?

  • 3-methylcrotonyl-CoA carboxylase 1
  • 3-methylcrotonyl-CoA carboxylase biotin-containing subunit
  • MCCA
  • MCCase subunit alpha
  • methylcrotonoyl-CoA carboxylase 1 (alpha)

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

What glossary definitions help with understanding MCCC1?

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 (
  • Obata K, Fukuda T, Morishita R, Abe S, Asakawa S, Yamaguchi S, Yoshino M, Ihara K, Murayama K, Shigemoto K, Shimizu N, Kondo I. Human biotin-containing subunit of 3-methylcrotonyl-CoA carboxylase gene (MCCA): cDNA sequence, genomic organization, localization to chromosomal band 3q27, and expression. Genomics. 2001 Mar 1;72(2):145-52. (
  • 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