Dephosphorylation and reactivation of phosphorylated purified ox-kidney branched-chain dehydrogenase complex by co-purified phosphatase

Abstract

AbstractThe branched-chain 2 oxoacid dehydrogenase complex has been purified from well-washed ox-kidney mitochondria together with branched-chain dehydrogenase kinase. The complex was inactivated and phosphorylated by ATP in about 5 min at 30°C. After hydrolysis of ATP by a contaminating ATPase (5–10 min) the complex was dephosphorylated and reactivated. Dephosphorylation and reactivation were linearly correlated. Reactivation was dependent upon Mg2+ (K0.5 > 1 mM) and inhibited completely by 50 mM fluoride. Reactivation and dephosphorylation are attributed to a mitochondrial branched-chain dehydrogenase phosphatase