Purification and properties of phytate-specific phosphatase from Bacillus subtilis

Abstract

An enzyme which liberates Pi from myo-inositol hexaphosphate (phytic acid) was shown to be present in culture filtrates of Bacillus subtilis. It was purified until it was homogeneous by ultracentrifugation, but it still showed two isozymes on polyacrylamide gel electrophoresis. The enzyme differed from other previously known phytases in its metal requirement and in its specificity for phytate. It had a specific requirement for Ca²⁺ for its activity. The enzyme hydrolyzed only phytate and had no action on other phosphate esters tested. This B. subtilis phytase is the only known phytate-specific phosphatase. The products of hydrolysis of phytate by this enzyme were P_i and myo-inositol monophosphate. The enzyme showed optimum activity at pH 7.5. It was inhibited by Ba²⁺, Sr²⁺, Hg²⁺, Cd²⁺, and borate. Its activity was unaffected by urea, diisopropylfluorophosphate, arsenate, fluoride, mercaptoethanol, trypsin, papain, and elastase.