CYCLIC-NUCLEOTIDE PHOSPHODIESTERASE FROM LEMNA-PAUCICOSTATA - EFFECT OF CALMODULIN AND THEOPHYLLINE

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.