结合作用导致人胸苷磷酸化酶中存在远程[5'-3H]胸苷动力学同位素效应。
Binding causes the remote [5'-3H]thymidine kinetic isotope effect in human thymidine phosphorylase.
作者信息
Birck Matthew R, Schramm Vern L
机构信息
Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
出版信息
J Am Chem Soc. 2004 Jun 9;126(22):6882-3. doi: 10.1021/ja0492642.
The remote 5'-3H V/K kinetic isotope effect (KIE) observed in human thymidine phosphorylase (6.1%) is significantly larger than can be explained by the reaction chemistry. One hypothesis connects the 5'-3H KIE in purine nucleoside phosphorylase to that enzyme's SN1 transition state. The transition state of thymidine phosphorylase, however, is an SN2 nucleophilic displacement. Here we report equilibrium binding isotope effects sufficiently large to explain the presence of this substantial KIE in thymidine phosphorylase.
在人胸苷磷酸化酶中观察到的远程5'-3H V/K动力学同位素效应（KIE）（6.1%）显著大于反应化学所能解释的范围。一种假设将嘌呤核苷磷酸化酶中的5'-3H KIE与该酶的SN1过渡态联系起来。然而，胸苷磷酸化酶的过渡态是SN2亲核取代。在此，我们报告了足够大的平衡结合同位素效应，足以解释胸苷磷酸化酶中这种显著KIE的存在。
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