Role of mitochondrial transamination in branched chain amino acid metabolism.

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