SUMMARYSome of the variables influencing the stability of purified and unpurified spinach catalase during storage were evaluated in model systems. A purified preparation of spinach catalase was obtained from spinach leaves by comminution and extraction with phosphate buffer and extraction with n‐butanol, NH4)2SO4precipitation, (NH4)2SO4fractionation, dialysis, and lyophilization. The preparation had a Kat.‐f. of 3300 at pH 7.0. The stability of the enzyme in storage was influenced primarily by storage temperature, the pH of catalase solutions, and the activity of microorganisms. The enzyme concentration had a relatively minor effect on catalase stability. The stability of spinach catalase during storage was not influenced by the presence of NaCl, sucrose, starch, and denatured catalase in catalase solutions; the atmospheric pressure under which solutions were stored: or differences in freezing ra
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