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BCKDHA gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

BCKDHA gene

The BCKDHA gene provides instructions for creating a critical component of an enzyme complex responsible for breaking down specific amino acids essential for energy production.

Normal Function

The BCKDHA gene provides instructions for making the alpha subunit of a group of enzymes called the branched-chain alpha-keto acid dehydrogenase (BCKD) enzyme complex. Two alpha subunits connect with two beta subunits (produced from the BCKDHB gene) to form the E1 component of this complex.

The BCKD enzyme complex is responsible for a key step in the breakdown of three protein building blocks (amino acids): leucine, isoleucine, and valine. These amino acids are obtained from protein-rich foods such as meat, milk, and eggs. The complex is active in mitochondria, the energy-producing centers of cells, where it helps convert these amino acids into molecules used for energy.

Health Conditions Related to Genetic Changes

Maple syrup urine disease

More than 80 mutations in the BCKDHA gene have been identified in individuals with maple syrup urine disease. These mutations typically cause the severe, classic form of the disorder, which appears shortly after birth.

  • Symptoms: The condition is named for the distinctive sweet odor of an affected infant's urine. Other symptoms include poor feeding, vomiting, lethargy, abnormal movements, and delayed development.
  • Mechanism: Mutations disrupt the function of the BCKD enzyme complex, preventing the effective breakdown of leucine, isoleucine, and valine. The resulting accumulation of these amino acids and their byproducts is toxic to cells and tissues, particularly in the nervous system, leading to seizures and developmental delays.
  • Specific Mutations: Most mutations change single amino acids. In the Old Order Mennonite population, a common mutation replaces the amino acid tyrosine with asparagine at position 438 (Tyr438Asn or Y438N).

Other Names for This Gene

  • BCKDE1A
  • BCKDH E1-alpha
  • branched chain keto acid dehydrogenase E1, alpha polypeptide (maple syrup urine disease)
  • MSUD1
  • ODBA_HUMAN

Frequently Asked Questions

Rapid intervention is critical. Immediate hospitalization, intravenous dextrose (10 % or higher) to suppress catabolism, and a BCAA‑free amino‑acid solution are administered. Hemodialysis or continuous renal replacement therapy may be used if plasma leucine exceeds > 1000 µmol/L or neurologic status deteriorates. Once stabilized, the patient is transitioned back to the individualized low‑BCAA diet under close metabolic‑clinic follow‑up.
Most newborn screening programs measure elevated leucine (or all branched‑chain amino acids) by tandem mass spectrometry. A positive screen prompts confirmatory plasma amino‑acid quantification and urine organic‑acid analysis, which reveal a characteristic pattern of branched‑chain keto‑acids. If biochemical results are consistent with MSUD, molecular testing—usually a targeted BCKDHA/BCKDHB/DBT gene panel or whole‑exome sequencing—is performed to identify the causative mutation.
The cornerstone is a lifelong protein‑restricted diet that limits leucine, isoleucine, and valine. Specialized medical formulas low in branched‑chain amino acids provide essential nutrients while preventing toxic accumulation. Frequent monitoring of plasma BCAA levels (often weekly in infancy, then monthly) guides adjustments. During growth spurts or illness, caloric intake may need to be increased to avoid catabolism.
Orthotopic liver transplantation can provide a permanent source of functional BCKD enzyme, effectively curing the metabolic defect. Candidates are typically those with frequent decompensations despite optimal medical management. Post‑transplant, most patients achieve normal plasma BCAA levels and can liberalize their diet, though lifelong immunosuppression is required. Long‑term survival rates exceed 80 % at 5 years, but careful selection and multidisciplinary care are essential.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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