The Calf Intestinal Alkaline Phosphatase. II. Reaction between the metal content and the enzyme activity

Pure alkaline phosphatase (EC 3.1.3.1; 1500 U/mg) was dialyzed at 4° during 168 h against water, 10^?4M EDTA or 10^?4M o-phenanthroline. During the dialysis, samples were periodically removed and analyzed for metal content and activity. The results indicate that 1 mol of native calf intestinal alkaline phosphatase contains 4 g-atom of zinc and 4 g-atom of magnesium tightly bound, and that both metal ions are necessary for full enzyme activity. The dialyzed, partially demetallized enzyme could be reactivated by the addition of zinc and/or magnesium salts.