title: Control of guanylate cyclase activity in the rod outer segment.
abstract: 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.
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D006152:Cyclic GMP / Q000096:biosynthesis; D006160:Guanosine Triphosphate / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008027:Light; D010761:Phosphorus Radioisotopes; D010786:Photoreceptor Cells / Q000201:enzymology*
chemical_list: D010761:Phosphorus Radioisotopes; D006160:Guanosine Triphosphate; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D002118:Calcium