Ota A, Yoshida S, Nagatsu T
Joint Research Division for Therapies against Intractable Diseases, School of Medicine, Fujita Health University, Aichi, Japan.
J Neural Transm (Vienna). 1996;103(12):1415-28. doi: 10.1007/BF01271255.
The N-terminal 52-, 70-, and 157-amino acids-deleted mutants and wild-type tyrosine hydroxylases were expressed in Escherichia coli and utilized to investigate the roles of the N-terminus in the catecholamine inhibition on enzyme activity. Their lysate's supernatants were used as enzyme samples. Three catecholamines, namely dopamine, norepinephrine, and epinephrine, affected both wild-type and mutant enzymes after preincubation in the mode of mixed inhibition, and the most marked alteration among the kinetic parameters produced by the deletion was the increase in the inhibition constants. The deletions also abolished the catecholamine-induced shift of the pH profile of the enzyme activity toward a more acidic pH optimum. All three mutants responded to catecholamines almost in the same way. These results suggest that the three catecholamine end products exert their inhibition on tyrosine hydroxylase to the same extent and that the N-terminal 52 amino acid residues contain the key sequence in mediating the inhibitory action.
将N端缺失52个、70个和157个氨基酸的突变体以及野生型酪氨酸羟化酶在大肠杆菌中表达，并用于研究N端在儿茶酚胺对酶活性抑制作用中的作用。它们裂解物的上清液用作酶样品。三种儿茶酚胺，即多巴胺、去甲肾上腺素和肾上腺素，在以混合抑制模式预孵育后对野生型和突变型酶均有影响，缺失导致的动力学参数中最显著的变化是抑制常数增加。这些缺失还消除了儿茶酚胺诱导的酶活性pH谱向更酸性的最适pH值的偏移。所有三个突变体对儿茶酚胺的反应几乎相同。这些结果表明，三种儿茶酚胺终产物对酪氨酸羟化酶的抑制程度相同，并且N端的52个氨基酸残基包含介导抑制作用的关键序列。
