FUNCTIONAL REGULATION OF RECONSTITUTED NA,K-ATPASE BY PROTEIN-KINASE-A PHOSPHORYLATION

Reconstituted Na+,K+-ATPase from either pig kidney or shark rectal gla nds was phosphorylated by cAMP dependent protein kinase, PKA. The stoi chiometry was similar to 0.9 mole P-i/mole alpha-subunit in the pig ki dney enzyme and similar to 0.2 mol P-i/mol alpha-subunit in the shark enzyme, In shark Na+, K+-ATPase PKA phosphorylation increased the maxi mum hydrolytic activity for cytoplasmic Na+ activation and extracellul ar K+ activation without affecting the apparent K-m values, In contras t, no significant functional effect after PKA phosphorylation was obse rved in pig kidney Na+,K+-ATPase.