Light-regulated guanosine 3',5'-monophosphate phosphodiesterase of bovine retina.

RETINAL rod outer segment (ROS) adenyl cyclase activity seems to be light sensitive, implicating adenosine 3′,5′-monophosphate (cyclic AMP) in photoreceptor function1,2. Guanosine 3′,5′-monophosphate (cyclic GMP) could also play a role in photoreceptor function since the synthetic (guanyl cyclase)3 and degradative (cyclic GMP phosphodiesterase)4 enzymes are highly active in purified ROS. In particular the specific activity of guanyl cyclase is higher in bovine photoreceptor structures than in any other tissue studied. This activity, however, is not influenced by illumination3.