2',3'-Cyclic nucleotide 2'-phosphodiesterase from Fusarium culmorum

Abstract We describe the properties of a 2′,3′-cyclic nucleotide 2′-phosphodiesterase (EC 3.1.4.16), found in Fusarium culmorum, which hydrolyzes nucleoside 2′,3′-cyclic monophosphates to nucleoside 3′-phosphates. In contrast with a similar enzyme found in bacteria, the Fusarium enzyme does not exhibit nucleotidase activity and does not show a requirement for metal ions, but is inhibited by micromolar concentrations of Cu ++ and Zn ++ , and is very stable to heat. This cyclic phosphodiesterase hydrolyzes the four major nucleoside 2′,3′-cyclic monophosphates and has greater affinity for purine ( K m s for Ado-2′,3′-P=0.3 mM and for Guo-2′,3′-P=0.1 mM) than for pyrimidine nucleotides ( K m s for Cyd-2′,3′-P=0.6 mM and for Urd-2′,3′-P=2 mM). The respective V max for Urd-2′,3′-P; Cyd-2′,3′-P; Ado-2′,3′-P; and Guo-2′,3′ are 100:45:16:5. The efficacy of the phosphodiesterase to hydrolyze the four major 2′,3′ cyclic nucleotides (based on the relative values of V max / K m ) is not significantly different. The Fusarium enzyme differs from a previously described 2′,3′ cyclic phosphodiesterase from Neurospora , in that it is inactive on 3′,5′-nucleoside monophosphates and nucleoside 2′ or 3′ phosphates.