Glutamic Acid Decarboxylase of Squash and Radish

1. Glutamic acid decarboxylase is more abundant near the surface than in the central portion of the radish hypocotyl, and it accumulates in mature and senescent radish leaves. There was essentially no effect of boron nutrition on enzyme activity. 2. Squash decarboxylase was partially purified by lyophilization, freezing in solution, precipitation in cold acetone, ammonium sulfate precipitation, or by combinations of these. 3. The enzyme was irreversibly inactivated at pH values outside the range 5.7-6.2 and at temperatures above about 54⚬C. 4. The enzyme lost coenzyme easily during processing or by dialysis but was reactivated with synthetic pyridoxal phosphate.