Cyclic nucleotide phosphodiesterase in pea seedlings

Abstract

An enzyme from pea seedlings that hydrolyzes both 2′,3′-cyclic nucleoside monophosphate and 3′,5′-cyclic nucleoside monophosphate has been partially purified from pea seedlings. It has a molecular weight of 350 000 and has optimal activity at pH 5.4–6.0. It is insensitive to methylxanthines and imidazole. It catalyzes the formation of 3′-AMP exclusively from 2′,3′-cyclic AMP and the formation of 3′-AMP and 5′-AMP from 3′,5′-cyclic AMP. The ratio of 3′-AMP to 5′-AMP in the latter case is 7 to 1. The activities toward 2′,3′-cyclic AMP and 3′,5′-cyclic AMP are quite similarly affected by pH, metal ions, sulfhydryl reagents, temperature, and urea. Furthermore, the two activities have identical physical properties. It is suggested, therefore, that a single enzyme molecule is responsible for both activities.