THE PYRUVATE-DEHYDROGENASE COMPLEX OF SACCHAROMYCES-CEREVISIAE IS REGULATED BY PHOSPHORYLATION

Mitochondria mere isolated from Saccharomyces cerevisiae grown on different carbon sources prior to incubation with [gamma-P-32]ATP, A major 46,000-M(r) phosphoprotein, corresponding in M(r) value to the El alpha subunit of the yeast pyruvate dehydrogenase complex (PDC), was detected only in mitochondria isolated from cells grown on a fermentable carbon source such as galactose, Immunoprecipitation with subunit-specific antiserum to the E1 component of mammalian or yeast PDC confirmed the identity of this polypeptide. PDC activity in isolated yeast mitochondria could be inactivated in an ATP-dependent fashion and reactivated in the presence of Ca2+ ions.