REGULATION OF CYCLIC NUCLEOTIDE CONCENTRATIONS IN PHOTORECEPTORS - ATP-DEPENDENT STIMULATION OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASE BY LIGHT
REGULATION OF CYCLIC NUCLEOTIDE CONCENTRATIONS IN PHOTORECEPTORS - ATP-DEPENDENT STIMULATION OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASE BY LIGHT
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DOI：
10.1073/pnas.70.12.3820
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发表时间：
1973-01-01
影响因子：
11.1
通讯作者：
BITENSKY, MW
中科院分区：
文献类型：
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作者：
MIKI, N;KEIRNS, JJ;BITENSKY, MW
环核苷酸浓度的调节杆外节（蛙尖音）已被进一步研究。目前的研究表明，照明显着减少感光膜悬浮液中的环核苷酸的浓度，但调节的位点是环核苷酸磷酸二酯酶（EC 3.1.4.c）（光刺激），而不是腺苷酸环化酶。视紫红质的漂白作用与磷酸二酯酶的刺激作用之间存在着明显的相关性。仅漂白0.6%的视紫红质产生的刺激是漂白100%视紫红质产生的刺激的一半。光激活磷酸二酯酶的过程分为两个步骤，一个光依赖性步骤，然后是ATP依赖性步骤。光照（在没有ATP的情况下）产生一种抗胰蛋白酶的、不耐热的大分子刺激物。在0.75 mM ATP（GTP或ITP）存在下，这种刺激剂使感光细胞磷酸二酯酶的Vmax增加5倍以上，而不改变Km。在生理底物浓度（10- 7 M）的环GMP的水解率是23倍以上的环AMP。光产生的刺激物似乎是感光膜所特有的，并且不会激活其他组织中的磷酸二酯酶。
Regulation of cyclic nucleotide concentrations in rod outer segments (Rana pipiens) has been further examined. The present studies show that illumination markedly diminishes the concentration of cyclic nucleotides in suspensions of photoreceptor membranes, but the locus of regulation is cyclic nucleotide phosphodiesterase (EC 3.1.4.c) (light-stimulated) and not adenylate cyclase. There is a marked disproportionality between bleaching of rhodopsin and stimulation of phosphodiesterase. Bleaching only 0.6% of the rhodopsin produces half the stimulation produced by bleaching 100% of the rhodopsin. The process of activation of phosphodiesterase by light is in two steps, a light-dependent step followed by an ATP-dependent step. Illumination (in the absence of ATP) produces a trypsin-resistant, heat-labile, macromolecular stimulator. In the presence of 0.75 mM ATP (GTP or ITP) this stimulator produces a greater than 5-fold increases in theVmaxof photoreceptor phosphodiesterase without changing theKm. At physiological substrate concentrations (10-7M) the rate of hydrolysis of cyclic GMP is 23 times greater than that of cyclic AMP. The light-produced stimulator appears unique to the photoreceptor membranes and does not activate phosphodiesterase in other tissues.