PURIFICATION AND SOME PROPERTIES OF MEMBRANE-BOUND AND SOLUBLE PYROPHOSPHATASES OF YEAST VACUOLES

The membrane-bound and soluble pyrophosphatase (PPase) activities of Saccharomyces carlsbergensis vacuoles are determined by the functioning of special enzymes and are not due to non-specific PP(i) hydrolysis by other vacuolar phosphohydrolases. The molecular mass of the membrane-bound PPase is apparently 120 000 and its molecule consists of three subunits with M(r) = 41 000. Soluble PPase has a molecular mass of about 82 000 and includes three subunits with M(r) = 28 000. Both enzymes are glycoproteins. The vacuolar membrane-bound PPase is a proton pump.