Acetyl phosphatase in brain microsomes: A partial reaction of Na + + K + ATPase

Abstract

A K +-stimulated acetyl phosphatase has been described in brain microsomes. On the basis of ouabain, Ca ++, SH inhibitor sensitivity, and nucleotide inhibition, it is considered that this reaction reflects the terminal stage of the Na + and K + ATPase. From labeling studies, and from comparison with the properties of the K +-stimulated fraction of p-nitrophenol phosphatase, a tentative scheme is proposed suggesting two phosphorylated protein intermediates in the ATPase reaction, a protein-bound carboxyl phosphate, and a second lower energy ester.