Light onset stimulates tyrosine hydroxylase activity in isolated teleost retinas.
Light onset stimulates tyrosine hydroxylase activity in isolated teleost retinas.
复制标题
光照刺激离体硬骨鱼视网膜中酪氨酸羟化酶的活性。
DOI：
10.1016/0042-6989(91)90092-j
复制
发表时间：
1991
期刊：
影响因子：
1.8
通讯作者：
Dearry,A
中科院分区：
文献类型：
--
作者：
Dearry,A
酪氨酸羟化酶的作用是合成多巴胺的限速步骤，多巴胺是脊椎动物视网膜中含量最丰富的儿茶酚胺。我研究了这种酶在绿色太阳鱼Lepomis Bluellus的视网膜中的激活和调节。将先前适应黑暗的视网膜暴露在持续光照10分钟的时间内，酶活性是在黑暗中孵化的视网膜的2.2倍。因此，光的到来激活了硬骨视网膜中的酪氨酸羟基酶。在这些条件下，酪氨酸羟基酶活性的刺激与其蝶啶辅因子酶的表观Km的降低有关，而反应的表观Vmax不变。这一结果表明，短期的光照通过增强酶对其自然产生的辅因子的亲和力来增加多巴胺的合成。这些发现与光激活硬骨视网膜中的多巴胺能神经元的想法是一致的。
The action of tyrosine hydroxylase is the rate-limiting step in the synthesis of dopamine, the most abundant catecholamine in vertebrate retinas. I have examined the activation and regulation of this enzyme in isolated retinas of green sunfish,Lepomis cyanellus.Exposing previously dark-adapted retinas to constant illumination for a period of 10 min increased enzymatic activity 2.2-fold over that present in retinas incubated in darkness. Thus, light onset activates tyrosine hydroxylase in teleost retinas. Stimulation of the activity of tyrosine hydroxylase under these conditions was associated with a decrease in the apparentKmof the enzyme for its pteridine cofactor without a change in the apparentVmaxof the reaction. This result suggests that short-term exposure to light increases dopamine synthesis by enhancing the affinity of the enzyme for its naturally occurring cofactor. These findings are consistent with the idea that light activates dopaminergic neurons in teleost retinas.