Effects of nucleotides and nucleosides on the activity of cyclic AMP phosphodiesterase from rat brain.

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Abstract
Cyclic nucleotides phosphodiesterase (PDE) was prepared from cerebrum of male rats and its kinetic properties were studied. The phosphodiesterase preparation exhibited 2 Km, 8.7 .mu.M and 83.3 .mu.M. Adenine derivatives such as adenosine, 5''-AMP and 2''(3'')-AMP inhibited the PDE activity at concentrations exceeding 7 .times. 10-3 M, and 2''-deoxyadenosine inhibited the activity at lower concentrations (Ki = 1.8 .times. 10-3 M). Guanine derivatives showed several different effects. Guanosine and 3'',5''-cGMP activated the PDE at 10-5 M and inhibited at concentrations > than 10-4M. 2''(3'')-GMP showed no effect, but 5''-GMP activated markedly at concentrations of 10-3 to 10-2 M. Thymidine showed slight inhibitory effect, but cytidine or 2''-deoxycytidine had no effect. Uracil derivatives such as uridine, 5''-UMP, 3'',5''-cUMP and 2''(3'')-UMP activated the PDE at concentrations exceeding 3 .times. 10-3 M. Individual nucleosides and nucleotides exhibit structure-activity relationship with PDE.