CHARACTERIZATION OF POLYPHOSPHATASE ACTIVITY OF VACUOLES OF THE YEASTSACCHAROMYCES-CEREVISIAE

Vacuoles of the yeast Saccharomyces cerevisiae possess a polyphosphata se activity which differs from other known vacuolar phosphohydrolase a ctivities in pH optimum, sensitivity towards inhibitors, and distribut ion between the vacuolar sap and tonoplast. The polyphosphatase activi ty is inhibited by EDTA, ammonium molybdate, orthovanadate, and fluori de. Nearly 77% of this activity is located in the vacuolar sap and 25% in the tonoplast fraction. Both soluble and membrane-bound polyphosph atase activities are maximal at pH 6.8-7.2. Bivalent metal cations sti mulate this activity in the following order: Zn2+ > Mg2+ > Co2+ > Mn2, while Fe2+, CU2+,and Ca2+ inhibit this activity at all concentration s tested The polyphosphatase activity of both vacuolar sap and tonopla st increases by 2.4 and 2 times, respectively, with the increase in th e degree of polymerization of polyphosphate from (n) over bar = 3 to ( n) over bar = 208.