Enzymatic Breakdown of Polymetaphosphate. V. Purification and Specificity of the Enzyme.

Abstract

When Aspergillus niger was cultured at 30[degree] for 4-6 days, most of the polymetaphosphatase activity was in the medium. The substrate was a polymetaphosphate (KPO3)n whose mol. wt. was greater than 106, and activity was measured by the viscosity change in the colloidal substrate. Purification of the enzyme involved precipitation with (NH4)2SO4 and electrophoresis. Although the prepn. was homogeneous in the ultracentrifuge and had measurable activity in concn. of 6 x 10-5 mg. N/ml., it was contaminated with other phosphatases which have the same solubility properties and electrophoretic migration. Evidence for the existence of a specific polymetaphosphatase was obtained by comparison of pH-optima and of conditions of activation and inhibition. The polymetaphosphatase was activated by Mn++ and Zn++ but not the other phosphatases. The latter were inhibited by F ions, but not polymetaphosphatase. The occurrence of metaphosphatases in higher organisms is briefly considered.