Cyclic nucleotide phosphodiesterase from Lemna paucicostata: Effect of Calmodulin and theophylline

Abstract

Cyclic nucleotide phosphodiesterase has been purified partially from aseptically grown Lemna paucicostata 6746 by ammonium sulphate fractionation and gel filtration chromatography on Sephadex G-200. The activity and substrate specificity of this partially purified enzyme has been determined by resolving the hydrolysed nucleotides employing ion-pair reverse-phase HPLC. The enzyme preparation showed higher activity towards 2′,3′-cyclic nucleotides than towards 3′,5′-cyclic nucleotides and adenine derivatives were relatively more sensitive to Lemna phosphodiesterase than guanine derivatives. Calmodulin was found to stimulate the enzyme activity both towards 2′,3′- and 3′,5′-isomers, whereas theophylline inhibited the enzyme activity towards 3′,5′-cyclic nucleotides. The hydrolysis products of 3′,5′-cyclic nucleotides and their 2′,3′-isomers were identified as 5′- and 3′-nucleotides, respectively.