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 Pi 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.

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I956 5. The countercurrent-distribution technique has also been used for studies of the action of aqueous HCI on protoporphyrin and its methyl ester. We thank Professor C. Rimington, F.R.S., for his continuous encouragement and support and Miss B. E. Tooth for technical assistance. We are grateful to B. Lewis and Co. for generous supplies of chicken blood. During part of the time that this work was carried out, one of us (J.E.F.) held a Foulerton Research Fellowship of the Royal Society. The Nuffield Unit is supported by a grant from the Nuffield Foundation to Professor C. Rimington.

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