Functional regulation of reconstituted Na, K‐ATPase by protein kinase A phosphorylation

Abstract

Reconstituted Na⁺,K⁺‐ATPase from either pig kidney or shark rectal glands was phosphorylated by cAMP dependent protein kinase, PKA. The stoichiometry was ∼ 0.9 mole P_i/mole α‐subunit in the pig kidney enzyme and ∼ 0.2 mol P_i/mol α‐subunit in the shark enzyme. In shark Na⁺,K⁺‐ATPase PKA phosphorylation increased the maximum hydrolytic activity for cytoplasmic Na⁺ activation and extracellular K⁺ activation without affecting the apparent K _m values. In contrast, no significant functional effect after PKA phosphorylation was observed in pig kidney Na⁺,K⁺‐ATPase.