Human mutations affecting branched chain alpha-ketoacid dehydrogenase

Area of Science:

• Biochemistry
• Genetics
• Metabolic Disorders

Background:

• Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder caused by defects in the branched-chain alpha-ketoacid dehydrogenase complex (BCKD).
• Over 50 mutations in three genes affecting BCKD function are known, with a higher incidence in specific populations like Mennonites.
• The BCKD complex is crucial for amino acid metabolism and is located within mitochondria, with its activity regulated by phosphorylation.

Purpose of the Study:

• To investigate the molecular mechanisms underlying transcription, translation, protein import, and assembly of the BCKD complex.
• To elucidate the long-term pathophysiology of BCKD dysfunction.
• To understand the role of BCKD in regulating leucine levels, protein metabolism, and hormone release.

Main Methods:

• Analysis of naturally occurring mutations in genes encoding BCKD components.
• Study of mitochondrial protein import and complex assembly processes.
• Investigation of BCKD regulation by phosphorylation and its relationship with metabolic and hormonal factors.

Main Results:

• Identification of over 50 causal mutations across three genes essential for BCKD catalytic function.
• Understanding of BCKD's presence in all mammalian cells with mitochondria and its regulation via a complex-specific kinase.
• Insights into the molecular basis of BCKD dysfunction and its genetic underpinnings.

Conclusions:

• BCKD defects lead to Maple syrup urine disease, highlighting the importance of this complex in amino acid metabolism.
• Naturally occurring mutations provide valuable models for studying fundamental molecular processes.
• Further research is needed to fully explain the long-term consequences of BCKD dysfunction and its broader metabolic regulatory roles.