Cyclic-GMP Phosphodiesterase in Photoreceptor Cells in Limulus Ventral Eye
The cyclic-GMP phosphodiesterase (PDE) in Limulus ventral eyes was found to have the following characteristics. The PDE required magnesium (or manganese ions) for maximal activity. The Km for cyclic-GMP was 0.5 μM. Light diminished the PDE activity; the Light/Dark ratio was about 0.79 (for 2 × 10−4 W/cm2 steady illumination). Addition of 0.01 mM GTP or GTP γ S increased the effect of illumination. The light-induced diminution was blocked by 0.1 mM GDP β S. These data suggests that light modulates cyclic-GMP PDE through a G-protein in Limulus ventral eyes.
KeywordsGuanylate Cyclase Phosphodiesterase Activity Photoreceptor Membrane Vertebrate Photoreceptor Steady Illumination
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