Purification and characterization of an exopolyphosphatase from Saccharomyces cerevisiae.

An exopolyphosphatase (polyphosphate phosphohydrolase; EC 3.6.1.11) activity that cleaves inorganic polyphosphates to orthophosphate has been purified to apparent homogeneity (> 95% pure) from Saccharomyces cerevisiae. The exopolyphosphatase is a monomeric protein with a polypeptide molecular mass of 28 kDa. The enzyme, which can be stabilized in the presence of Triton X-100, has a pH optimum of 7.5 and requires, for maximal activity, Co2+ or Mg2+ ions. In the absence of these ions, the exopolyphosphatase binds to polyphosphate but does not degrade it, allowing affinity purification of the enzyme on a polyphosphate-modified zirconia support. o-Vanadate, Cu2+, and Ca2+ are effective inhibito…