PURIFICATION AND PROPERTIES OF EXOPOLYPHOSPHATASE ISOLATED FROM SACCHAROMYCES-CEREVISIAE VACUOLES

An exopolyphosphatase (polyPase) with a specific activity of 60 U/mg p rotein has been purified from the vacuolar sap of Saccharomyces cerevi siae. The molecular mass of the intact enzyme was found to be 245 kDa, It is highly specific towards high-molecular polyphosphates (polyP), The activity with polyP(9) is 24% of that with polyP(208). The apparen t K-m for polyP(15) and polyP(208) hydrolysis is 93 and 2.4 mu M, resp ectively. The enzyme is slightly active with polyP(3) and adenosine-5' -tetraphosphate, but does not hydrolyze pyrophosphate, ATP, GTP and p- nitrophenylphosphate. It is stimulated by divalent metal cations, Co2 the best activator, stimulates it 6-fold. Antibodies that inhibit the cell envelope and cytosol polyPases of S. cerevisiae have no effect o n the vacuolar polyPase. The vacuolar polyPase differs from other yeas t polyPases in molecular mass, substrate specificity and effects of ac tivators. (C) 1998 Federation of European Biochemical Societies.