Cyclic nucleotide phosphodiesterase was purified from Rhizobium freddi MAR-1. The enzyme had a molecular weight of approximately 59,000 and was composed of a single subunit. The pH optimum of the enzyme was approximately 7.0 in both Tris-Cl and Imidazole buffers. However Imidazole buffer was shown to produce a two-fold stimulation of enzyme activity without affecting the pH optimum. Cyclic nucleotide phosphodiesterase from R. fredii MAR-1 was stable at 28°C for at least 10 days. The enzyme did not require any metal ion for activity although Cu2+ at 2.5 mM stimulated the enzyme. EDTA up to 2.5 mM did not inhibit the enzyme. Both NAD and NADP as well as FAD inhibited the enzyme with FAD showing maximum inhibition. The enzyme was able to hydrolyse both 3′,5′-cyclic AMP and 3′,5′-cyclic GMP but did not hydrolyse 2′,3′-cyclic AMP. The apparent Km of the enzyme for cAMP was approximately 0.1 μM.
- cAMP metabolism
- Cyclic nucleotide phosphodiesterase
- Rhizobium fredii