title: Activation of phosphodiesterase in frog rod outer segment by rhodopsin analogues.
abstract: Activation of guanosine 3',5'-cyclic monophosphate (cGMP) phosphodiesterase (EC 3.1.4.35) in frog rod outer segment membrane by rhodopsin analogues has been investigated. A rhodopsin analogue modified at the Schiff-base linkage (N-retinyl-opsin) or the beta-ionone ring (3-dehydro-rhodopsin) in the retinylidene chromophore of rhodopsin has some ability in activation of the enzyme. In consideration of our previous observation that opsin including a retinal-oxime can activate the enzyme, it seems likely that the Schiff-base linkage is not always necessary for the phosphodiesterase activation. On the other hand, a change in the length of the side chain of retinal (complex of opsin and beta-ionone, beta-ionylideneacetaldehyde or retinylideneacetaldehyde) or dissection of the conjugate double-bond system of the side chain (retro-gamma-rhodopsin) remarkably reduces the activation ability. However, 5,8-epoxy-rhodopsin having a similar dissected conjugate double-bond system induces some enzyme activation because of its rigid conformation around C7-C8-C9 single bonds. Consequently, it is suggested that the necessary portion of rhodopsin chromophore for the activation of the enzyme is the rigid conjugate double-bond system between the beta-ionone ring and the Schiff-base linkage in its all-trans form.
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D004789:Enzyme Activation / Q000187:drug effects; D008968:Molecular Conformation; D010786:Photoreceptor Cells / Q000201:enzymology*; D011892:Rana catesbeiana; D012168:Retinal Pigments / Q000494:pharmacology*; D012243:Rhodopsin / Q000031:analogs & derivatives / Q000494:pharmacology*; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D012545:Schiff Bases; D013329:Structure-Activity Relationship
chemical_list: D012168:Retinal Pigments; D012545:Schiff Bases; D012243:Rhodopsin; D015106:3',5'-Cyclic-GMP Phosphodiesterases