Role of mitochondrial transamination in branched chain amino acid metabolism

Journal Article · Tue Mar 15 04:00:00 EST 1988 · J. Biol. Chem.; (United States)

OSTI ID:5239036

Hutson, S M; Fenstermacher, D; Mahar, C

Oxidative decarboxylation and transamination of 1-/sup 14/C-branched chain amino and alpha-keto acids were examined in mitochondria isolated from rat heart. Transamination was inhibited by aminooxyacetate, but not by L-cycloserine. At equimolar concentrations of alpha-ketoiso(1-/sup 14/C)valerate (KIV) and isoleucine, transamination was increased by disrupting the mitochondria with detergent which suggests transport may be one factor affecting the rate of transamination. Next, the subcellular distribution of the aminotransferase(s) was determined. Branched chain aminotransferase activity was measured using two concentrations of isoleucine as amino donor and (1-/sup 14/C)KIV as amino acceptor. The data show that branched chain aminotransferase activity is located exclusively in the mitochondria in rat heart. Metabolism of extramitochondrial branched chain alpha-keto acids was examined using 20 microM (1-/sup 14/C)KIV and alpha-ketoiso(1-/sup 14/C)caproate (KIC). There was rapid uptake and oxidation of labeled branched chain alpha-keto acid, and, regardless of the experimental condition, greater than 90% of the labeled keto acid substrate was metabolized during the 20-min incubation. When a branched chain amino acid (200 microM) or glutamate (5 mM) was present, 30-40% of the labeled keto acid was transaminated while the remainder was oxidized. Provision of an alternate amino acceptor in the form of alpha-keto-glutarate (0.5 mM) decreased transamination of the labeled KIV or KIC and increased oxidation. Metabolism of intramitochondrially generated branched chain alpha-keto acids was studied using (1-/sup 14/C)leucine and (1-/sup 14/C)valine. Essentially all of the labeled branched chain alpha-keto acid produced by transamination of (1-/sup 14/C)leucine or (1-/sup 14/C)valine with a low concentration of unlabeled branched chain alpha-keto acid (20 microM) was oxidized.

• Research Organization: Pennsylvania State Univ., University Park (USA)
• OSTI ID: 5239036
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:8; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETATES
AMINO ACIDS
AMINOTRANSFERASES
ANIMALS
BIOLOGICAL MODELS
BODY
CARBON 14 COMPOUNDS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CHEMICAL REACTIONS
DECARBOXYLATION
DISTRIBUTION
ENZYME ACTIVITY
ENZYMES
HEART
INHIBITION
ISOTOPE APPLICATIONS
KETO ACIDS
LABELLED COMPOUNDS
LEUCINE
MAMMALS
MEMBRANE TRANSPORT
METABOLISM
MITOCHONDRIA
MUSCLES
MYOCARDIUM
NITROGEN TRANSFERASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
RATS
REDOX REACTIONS
RODENTS
SUBCELLULAR DISTRIBUTION
TRACER TECHNIQUES
TRANSFERASES
VALINE
VERTEBRATES