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


Reviewed December 2008

What is the official name of the BCKDHB gene?

The official name of this gene is “branched chain keto acid dehydrogenase E1, beta polypeptide.”

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

What is the normal function of the BCKDHB gene?

The BCKDHB gene provides instructions for making one part, the beta subunit, of an enzyme complex (a group of enzymes that work together). This complex is called branched-chain alpha-keto acid dehydrogenase, or BCKD. Two beta subunits connect with two alpha subunits, which are produced from the BCKDHA gene, to form a critical part of the enzyme complex called the E1 component.

The BCKD enzyme complex is responsible for one step in the normal breakdown of three protein building blocks (amino acids). These amino acids—leucine, isoleucine, and valine—are obtained from the diet. They are present in many kinds of food, particularly protein-rich foods such as milk, meat, and eggs. The BCKD enzyme complex is active in mitochondria, which are specialized structures inside cells that serve as energy-producing centers. The breakdown of leucine, isoleucine, and valine produces molecules that can be used for energy.

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

maple syrup urine disease - caused by mutations in the BCKDHB gene

More than 40 mutations in the BCKDHB gene have been identified in people with maple syrup urine disease, most often in individuals with the severe, classic form of the disorder. Some of these mutations change single amino acids in the beta subunit of the BCKD enzyme complex. A particular mutation is most common in people of Ashkenazi (eastern and central European) Jewish descent; this mutation replaces the amino acid arginine with the amino acid proline at position 183 in the beta subunit (written as Arg183Pro or R183P). Other BCKDHB mutations insert or delete small amounts of DNA in the gene.

Mutations in the BCKDHB gene disrupt the normal function of the BCKD enzyme complex, preventing it from effectively breaking down leucine, isoleucine, and valine. As a result, these amino acids and their byproducts build up in the body. This accumulation is toxic to cells and tissues, particularly in the nervous system. The buildup of these substances can lead to seizures, developmental delay, and the other medical problems associated with maple syrup urine disease.

Where is the BCKDHB gene located?

Cytogenetic Location: 6q14.1

Molecular Location on chromosome 6: base pairs 80,106,627 to 80,346,270

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

The BCKDHB gene is located on the long (q) arm of chromosome 6 at position 14.1.

The BCKDHB gene is located on the long (q) arm of chromosome 6 at position 14.1.

More precisely, the BCKDHB gene is located from base pair 80,106,627 to base pair 80,346,270 on chromosome 6.

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

Where can I find additional information about BCKDHB?

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

  • 2-oxoisovalerate dehydrogenase beta subunit
  • BCKDH E1-beta
  • branched chain keto acid dehydrogenase E1, beta polypeptide (maple syrup urine disease)
  • branched chain keto acid dehydrogenase E1, beta polypeptide precursor

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

What glossary definitions help with understanding BCKDHB?

acids ; amino acid ; arginine ; breakdown ; dehydrogenase ; developmental delay ; DNA ; enzyme ; gene ; isoleucine ; leucine ; mitochondria ; mutation ; nervous system ; precursor ; proline ; protein ; subunit ; toxic ; valine

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


  • Edelmann L, Wasserstein MP, Kornreich R, Sansaricq C, Snyderman SE, Diaz GA. Maple syrup urine disease: identification and carrier-frequency determination of a novel founder mutation in the Ashkenazi Jewish population. Am J Hum Genet. 2001 Oct;69(4):863-8. Epub 2001 Aug 16. (
  • Flaschker N, Feyen O, Fend S, Simon E, Schadewaldt P, Wendel U. Description of the mutations in 15 subjects with variant forms of maple syrup urine disease. J Inherit Metab Dis. 2007 Nov;30(6):903-9. Epub 2007 Oct 8. (
  • Henneke M, Flaschker N, Helbling C, Müller M, Schadewaldt P, Gärtner J, Wendel U. Identification of twelve novel mutations in patients with classic and variant forms of maple syrup urine disease. Hum Mutat. 2003 Nov;22(5):417. (
  • NCBI Gene (
  • Nellis MM, Danner DJ. Gene preference in maple syrup urine disease. Am J Hum Genet. 2001 Jan;68(1):232-7. Epub 2000 Dec 7. (
  • Quental S, Macedo-Ribeiro S, Matos R, Vilarinho L, Martins E, Teles EL, Rodrigues E, Diogo L, Garcia P, Eusébio F, Gaspar A, Sequeira S, Furtado F, Lança I, Amorim A, Prata MJ. Molecular and structural analyses of maple syrup urine disease and identification of a founder mutation in a Portuguese Gypsy community. Mol Genet Metab. 2008 Jun;94(2):148-56. doi: 10.1016/j.ymgme.2008.02.008. Epub 2008 Apr 2. (
  • Rodríguez-Pombo P, Navarrete R, Merinero B, Gómez-Puertas P, Ugarte M. Mutational spectrum of maple syrup urine disease in Spain. Hum Mutat. 2006 Jul;27(7):715. (


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: December 2008
Published: February 8, 2016