Cited by 107Biochemical Acid Research StudiesAmino Acid Enzymes and MetabolismMetabolism and Genetic Disorders

A Novel Branched-chain Amino Acid Metabolon

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Islam, Mohammad Mainul, Wallin, Reidar, Wynn, R. Max, Conway, Myra, Fujii, Hisao, Mobley, James A., Chuang, David T., Hutson, Susan M.·2007·Journal of Biological Chemistry

Abstract

The catabolic pathways of branched-chain amino acids have two common steps. The first step is deamination catalyzed by the vitamin B(6)-dependent branched-chain aminotransferase isozymes (BCATs) to produce branched-chain alpha-keto acids (BCKAs). The second step is oxidative decarboxylation of the BCKAs mediated by the branched-chain alpha-keto acid dehydrogenase enzyme complex (BCKD complex). The BCKD complex is organized around a cubic core consisting of 24 lipoate-bearing dihydrolipoyl transacylase (E2) subunits, associated with the branched-chain alpha-keto acid decarboxylase/dehydrogenase (E1), dihydrolipoamide dehydrogenase (E3), BCKD kinase, and BCKD phosphatase. In this study, we provide evidence that human mitochondrial BCAT (hBCATm) associates with the E1 decarboxylase component of the rat or human BCKD complex with a K(D) of 2.8 microM. NADH dissociates the complex. The E2 and E3 components do not interact with hBCATm. In the presence of hBCATm, k(cat) values for E1-catalyzed decarboxylation of the BCKAs are enhanced 12-fold. Mutations of hBCATm proteins in the catalytically important CXXC center or E1 proteins in the phosphorylation loop residues prevent complex formation, indicating that these regions are important for the interaction between hBCATm and E1. Our results provide evidence for substrate channeling between hBCATm and BCKD complex and formation of a metabolic unit (termed branched-chain amino acid metabolon) that can be influenced by the redox state in mitochondria.

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Crossref · 10.1074/jbc.m700198200

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  • The redox switch is important in regulating metabolite shuttling between the BCKD complex and GDH.

    “This redox switch is unique to these aminotransferases and has been shown to be important in regulating metabolite shuttling between the BCKD complex and GDH (Islam et al. 2007).”

    From Alzheimer’s disease: Targeting the glutamatergic system (2020) · cites this paper as Islam et al. 2007

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Authors
Islam, M. M., Wallin, R., Wynn, R. M., Conway, M., Fujii, H., Mobley, J. A., Chuang, D. T., & Hutson, S. M.
Affiliations
  • Wake Forest University Health Sciences (US)
  • The University of Texas Southwestern Medical Center (US)
  • University of Alabama at Birmingham (US)
Corresponding author
Hutson, Susan M.
Venue
Journal of Biological Chemistry
Publisher
Elsevier BV
Published
2007-04
Volume
282
Issue
16
Pages
11893-11903
ISSN
0021-9258 (ISSN-L)
OpenAlex
W2072156470
Cited by
107
References
70
Citations by year
2026: 2 · 2025: 1 · 2024: 6 · 2023: 4 · 2022: 6 · 2021: 4 · 2020: 6 · 2019: 7 · 2018: 3 · 2017: 9 · 2016: 8 · 2015: 5 · 2014: 6 · 2013: 4 · 2012: 4
FWCI
3.86
Type
journal article
Language
en
Open access
Locations
  • Journal of Biological Chemistry (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • UWE Research Repository (UWE Bristol) (submittedVersion, cc-by)
Funders
National Institute of Diabetes and Digestive and Kidney Diseases (DK34738, R01DK026758, DK26758)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Biochemical Acid Research Studies
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Amino Acid Enzymes and Metabolism
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Clinical Biochemistry › Metabolism and Genetic Disorders
Keywords
branched-chain amino acid aminotransferase, branched-chain α-keto acids, oxidative decarboxylation, substrate channeling, enzyme complex formation, CXXC motif, NADH, mitochondrial redox state, branched-chain amino acid catabolism, lipoamide dehydrogenase
MeSH terms
Amino Acids, Branched-Chain, Transaminases, Animals, Catalysis, Humans, Kinetics, Male, Mitochondria, Mitochondria, Liver, NAD, Recombinant Proteins, Rats, Sprague-Dawley, Protein Structure, Tertiary, Protein Interaction Mapping, Rats

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