Purification and properties of exopolyphosphatase isolated from Saccharomyces cerevisiae vacuoles

An exopolyphosphatase (polyPase) with a specific activity of 60 U/mg protein has been purified from the vacuolar sap of Saccharomyces cerevisiae. 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 apparent K-m for polyP(15) and polyP(208) hydrolysis is 93 and 2.4 mu M, respectively. 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 on the vacuolar polyPase. The vacuolar polyPase differs from other yeast polyPases in molecular mass, substrate specificity and effects of activators. (C) 1998 Federation of European Biochemical Societies.