Amide Metabolism in Higher Plants. III. Distribution of Glutamyl Tranferase and Glutamine Synthetase Activity.

Abstract

Glutamyl transferase, an enzyme which catalyzes an exchange between ammonia or hydroxylamine and the amide group of glutamine, was detected in 38 of 43 species of plants and microorganisms tested. Legume nodules, and leaves of Echinocystis fabacea and Cucurbita pepo were among the most active sources. There was considerable variation due to physiological factors such as nutrition and age of tissue. Both glutamyl transferase and glutamine synthetase activities are localized in the soluble cytoplasm, and they could not be separated by isoelectric fractionation procedures. The wide distribution of transferase activity indicates it is of general importance in plant metabolism. Inability to separate transferase and synthetase activities is consistant with the suggestion that they are functions of a single enzyme.