Phytase and acid phosphatase in the dwarf bean, Phaseolus vulgaris

Abstract

Some properties of a phytase preparation from P. vulgaris are reported. The enzyme has a pH optimum of 5.2, is inhibited by high substrate concentrations, and by p-chloromercuriben-zoate (95% at 0.1 mM) and F- ions (55% at 10 mM) but not by iodo-acetamide up to a concentration of 10 mM. It has Km 0.15 mM. The acid phosphatase, present in the phytase preparations, was separated from the latter enzyme by diethylaminoethylcellulose chromatography and purified 50-fold. This enzyme has a pH optimum at 6.0 in crude preparation, and at 5.5 after purification. The Km is 1.2 mM with phenyl phosphates substrate, and the enzyme does not have phytase activity. Phytase and acid phosphatase were assayed in the cotyledons of P. vulgaris during germination. Both enzymes increased in activity during the early stages, but later decreased.