Reversible phosphorylation of pyruvate dehydrogenase in rat skeletal-muscle mitochondria. Effects of starvation and diabetes

摘要: The total activity of pyruvate dehydrogenase (PDH) complex in rat hind-limb muscle mitochondria was 76.4 units/g mitochondrial protein. proportion the active form 34% (as isolated), 8-14% (incubation with respiratory substrates) and greater than 98% without substrates). Complex also inactivated by ATP presence oligomycin B carbonyl cyanide m-chlorophenylhydrazone. Ca2+ (which activates PDH phosphatase) or dichloroacetate inhibit kinase) each increased concentration a concentration-dependent manner oxidizing 2-oxoglutarate/L-malate. Values giving half-maximal activation were 10 nM-Ca2+, 3 mM-pyruvate 16 microM-dichloroacetate. Activation inhibited Na+ Mg2+. Mitochondria incubated [32P]Pi/2-oxoglutarate/L-malate incorporated 32P into three phosphorylation sites alpha-chain PDH; relative rates 1 2 3, dephosphorylation, 3. Starvation ( 48h ) induction alloxan-diabetes had no effect on skeletal-muscle mitochondria, but decreased 2-oxoglutarate/L-malate concentrations Ca2+, dichloracetate required for reactivation. In extracts kinase 2-3-fold 48 h starvation alloxan-diabetes, phosphatase unchanged.