麦芽糖假丝酵母中苯丙氨酸和酪氨酸生物合成酶对色氨酸的绝对依赖性。

Absolute dependence of phenylalanine and tyrosine biosynthetic enzyme on tryptophan in Candida maltosa.

作者信息

Bode R, Melo C, Birnbaum D

出版信息

Hoppe Seylers Z Physiol Chem. 1984 Jul;365(7):799-803. doi: 10.1515/bchm2.1984.365.2.799.

DOI:10.1515/bchm2.1984.365.2.799

Abstract

Candida maltosa synthesizes phenylalanine and tyrosine only via phenylpyruvate and p-hydroxyphenylpyruvate. Tryptophan is absolutely necessary for the enzymatic reaction of chorismate mutase and prephenate dehydrogenase; activity of prephenate dehydratase can be increased 2.5-fold in the presence of tryptophan. Activation of the chorismate mutase, prephenate dehydratase and prephenate dehydrogenase by tryptophan is competitive with respect to chorismate and prephenate with Ka 0.06mM, 0.56mM and 1.7mM. In addition tyrosine is a competitive inhibitor of chorismate mutase (Ki = 0.55mM) and prephenate dehydrogenase (Ki = 5.5mM).

摘要

麦芽糖假丝酵母仅通过苯丙酮酸和对羟基苯丙酮酸合成苯丙氨酸和酪氨酸。色氨酸对于分支酸变位酶和预苯酸脱氢酶的酶促反应绝对必要；在色氨酸存在的情况下，预苯酸脱水酶的活性可提高2.5倍。色氨酸对分支酸变位酶、预苯酸脱水酶和预苯酸脱氢酶的激活作用相对于分支酸和预苯酸具有竞争性，其解离常数（Ka）分别为0.06mM、0.56mM和1.7mM。此外，酪氨酸是分支酸变位酶（抑制常数Ki = 0.55mM）和预苯酸脱氢酶（抑制常数Ki = 5.5mM）的竞争性抑制剂。