Effect of Cyclic AMP‐Dependent Protein Phosphorylating Conditions on the pH‐Dependent Activity of Tyrosine Hydroxylase from Beef and Rat Striata
Effect of Cyclic AMP‐Dependent Protein Phosphorylating Conditions on the pH‐Dependent Activity of Tyrosine Hydroxylase from Beef and Rat Striata
复制标题
环 AMP 依赖性蛋白磷酸化条件对牛肉和大鼠纹状体酪氨酸羟化酶 pH 依赖性活性的影响
作者：
R. Pollock;G. Kapatos;S. Kaufman
摘要牛脑纹状体酪氨酸羟化酶（TH，EC 1.14.16.2）从丙酮粉末提取物中纯化23倍。如果用环AMP依赖性蛋白磷酸化系统处理该酶制剂，则酶活性的pH依赖性发生变化。在饱和四氢生物蝶呤（BH 4）浓度下的最适pH从低于pH 6移动至约pH 6.7。在pH 7时，活化主要表示为Vmax的增加，而在pH 6时，活化主要表示为蝶呤辅因子Km的降低。此外，即使使用对照酶，随着pH从6增加到中性，蝶呤辅因子的Km也急剧下降。用G-25葡聚糖凝胶处理的大鼠纹状体TH获得了类似的数据。使用大鼠纹状体突触体的实验表明，TH的磷酸化条件下的原位激活主要表现为多巴胺合成的最大速率的增加。这些结果表明，由环AMP依赖性蛋白磷酸化引起的TH活性变化在很大程度上取决于TH环境的pH值。
Abstract Tyrosine hydroxylase (TH, EC 1.14.16.2) from beef brain striata was purified 23‐fold from an extract of an acetone powder. If this enzyme preparation is treated with a cyclic AMP‐dependent protein phosphorylation system, there is a change in the pH dependence of the enzyme activity. The pH optimum at saturating tetrahydrobiopterin (BH4) concentration is shifted from below pH 6 to about pH 6.7. At pH 7, activation is expressed mainly as an increase in Vmax, whereas at pH 6, activation is expressed mainly as a decrease in Km for the pterin cofactor. Further, even with the control enzyme the Km for pterin cofactor declines precipitously as the pH is increased from 6 toward neutrality. Similar data were obtained with G‐25 Sephadex‐treated rat striatal TH. Experiments in which rat striatal synaptosomes were used demonstrated that the in situ activation of TH by phosphorylating conditions is expressed primarily as an increase in the maximum rate of dopamine synthesis. These results indicate that changes in TH activity caused by cyclic AMP‐dependent protein phosphorylation will depend to a large extent on the pH of the TH environment.
磷酸化条件对酪氨酸羟化酶活性的影响受到测定条件和脑区域的影响。
影响因子：
6.1
作者：
Acheson,AL;Kapatos,G;Zigmond,MJ
通讯作者：
Zigmond,MJ