[H+-ATPase and H+-pyrophosphatase in yeast vacuolar membrane]

Saccharomyces carlsbergenis vacuoles possess an ATPase activity differing from those of the well-known H(+)-ATPase of plasma membranes and mitochondria as well as from those of other phosphohydrolases. Yeast vacuolar ATPase represents an electrogenic H(+)-translocase. H(+)-ATPase was incorporated into a liposomal membrane in a functionally active form. Tonoplast ATPase did not form a phosphorylated intermediate. Purified vacuolar ATPase contained three major polypeptides with M(r) of 72, 62 and 16 kDa. S. carlsbergensis vacuoles also contained a pyrophosphatase (PPase) whose properties differed significantly from those of other vacuolar phosphohydrolases. Vacuolar membrane-bound PPase is a proton pump; its molecular mass is about 120 kDa. The enzyme molecule consists of three subunits, each of M(r) = 41 kDa. Soluble PPase from vacuolar sap has a molecular mass of about 82 kDa and consists of three subunits of M(r) = 28 kDa.