Control of Guanylate Cyclase Activity in the Rod Outer Segment

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Science  14 Dec 1973:
Vol. 182, Issue 4117, pp. 1138-1140
DOI: 10.1126/science.182.4117.1138


Mammalian photoreceptors contain a guanylate cyclase which has a high specific activity and is inhibited by exposure of the rod outer segment to light. Several minutes are required for this inhibition to take effect, indicating that it is not a step in visual excitation. The activity of the enzyme is sensitive to the concentration of calcium ion in the medium, suggesting that light-induced changes in calcium distribution in the photoreceptor could control guanylate cyclase activity.