title: Cyclic GMP stimulation of a light-activated ATPase in rod outer segments.
abstract: Rod outer segments (ROSs) of vertebrate photoreceptor cells have been reported to contain several enzyme systems including a dark, Ca2+-stimulated ATPase, a rhodopsin kinase, a phosphodiesterase and a GTPase, all of which are light-stimulated. Recently, Thacher has found a light-stimulated Mg2+-ATPase in frog ROSs while our own laboratory has identified a dark, Ca2+-inhibited Mg2+-ATPase in bovine ROSs. Here we extend our observations on the Mg2+-ATPase and demonstrate that flash illumination following the dark ATPase process stimulated ATPase activity at a rate considerably faster than the dark process. In addition, we find that both the dark and light stimulated ATPase activities are markedly enhanced by cyclic GMP and inhibited by Ca2+.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D006152:Cyclic GMP / Q000494:pharmacology*; D004789:Enzyme Activation; D007700:Kinetics; D008027:Light; D010786:Photoreceptor Cells / Q000201:enzymology*; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D012542:Scattering, Radiation
chemical_list: D000251:Adenosine Triphosphatases; D006152:Cyclic GMP