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  • Title: Mitochondrial 2-oxoacid dehydrogenase complexes of animal tissues.
    Author: Randle PJ.
    Journal: Philos Trans R Soc Lond B Biol Sci; 1983 Jul 05; 302(1108):47-57. PubMed ID: 6137008.
    Abstract:
    The pyruvate dehydrogenase and branched-chain 2-oxoacid dehydrogenase complexes of animal mitochondria are inactivated by phosphorylation of serine residues, and reactivated by dephosphorylation. In addition, phosphorylated branched-chain complex is reactivated, apparently without dephosphorylation, by a protein or protein-associated factor present in liver and kidney mitochondria but not in heart or skeletal muscle mitochondria. Interconversion of the branched-chain complex may adjust the degradation of branched-chain amino acids in different tissues in response to supply. Phosphorylation is inhibited by branched-chain ketoacids, ADP and TPP. The pyruvate dehydrogenase complex is almost totally inactivated (99%) by starvation or diabetes, the kinase reactions being accelerated by products of fatty acid oxidation and by a protein or protein-associated factor induced by starvation or diabetes. There are three sites of phosphorylation, but only sites 1 and 2 are inactivating. Site 1 phosphorylation accounts for 98% of inactivation except during dephosphorylation when its contribution falls to 93%. Sites 2 and 3 are only fully phosphorylated when the complex is fully inactivated (starvation, diabetes). Phosphorylation of sites 2 and 3 inhibits reactivation by phosphatase. The phosphatase reaction is activated by Ca2+ (which may mediate effects of muscle work) and possibly by uncharacterized factors mediating insulin action in adipocytes.
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