PROTEIN KINASE-DEPENDENT PHOSPHORYLATION OF H,K ATPASE-CONTAINING MEMBRANES FROM RAT AND PIG STOMACHS

Previously H,K ATPase preparations from pig stomach were shown to cont ain intrinsic protein kinase activities which phosphorylated specific tyrosine and serine residues in the N;terminal of the a-chain of H,K A TPase (Togawa et al. 1996). in the present investigation, pig H,K ATPa se-containing membrane preparations were compared with rat preparation s. In contrast to results obtained with the a-subunit of H,K ATPase fr om pig, phosphorylation was not observed in the rat enzyme. Addition o f rat preparations to the pig preparations resulted in decreased phosp horylation in pig preparations. To follow the phosphorylation of membr ane proteins in vivo, P-32-loaded gastric cells prepared from rat were stimulated with several secretagogues. Proteins with molecular weight s of about 120 and 80 kDa were markedly phosphorylated upon stimulatio n, but the alpha-subunit of H,K ATPase was not. These results suggest that phosphorylation of tyrosine or serine residues of H,K ATPase foun d in pig H,K ATPase preparations may not be involved in the acid secre tion pathway.