Activation of R235A Mutant Orotidine 5′-Monophosphate Decarboxylase by the Guanidinium Cation: Effective Molarity of the Cationic Side Chain of Arg-235

被引：35

作者：

Barnett, Shonoi A. ^{[1
]}

Amyes, Tina L. ^{[1
]}

Wood, B. McKay ^{[2
,3
]}

Gerlt, John A. ^{[2
,3
]}

Richard, John P. ^{[1
]}

机构：

[1] SUNY Buffalo, Dept Chem, Buffalo, NY 14260 USA

[2] Univ Illinois, Dept Biochem, Urbana, IL 61801 USA

[3] Univ Illinois, Dept Chem, Urbana, IL 61801 USA

来源：

BIOCHEMISTRY | 2010年 / 49卷 / 05期

基金：

美国国家卫生研究院;

关键词：

PHOSPHITE DIANION; SUBSTRATE; CATALYSIS; ENZYME;

D O I：

10.1021/bi902174q

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 ; 081704 ;

摘要：

The R235A mutation at yeast orotidine 5'-monophosphate decarboxylase (OMPDC results in a 1300-fold increase in K(m) and a 14-fold decrease in k(cat) for decarboxylation of orotidine 5'-monophosphate, corresponding to a 5.8 kcal/mol destabilization of the transition state. There is strong activation of this mutant enzyme by added guanidinium cation (Gua(+)): 1 M Gua(+) stabilizes the transition state by ca. 3 kcal/mol. This stabilization is due to the binding of Gua(+) to the binary E(mut).OMP complex, witha K(d) of 50 mM, to form the 9-fold more reactive ternary E(mut).OMP.Gua(+) complex. The "effective molarity" of the cationic side chain of Arg-235 at the wild-type enzyme is calculated to be 160 M.

引用

页码：824 / 826

页数：3

共 14 条

[1] Formation and stability of a vinyl carbanion at the active site of orotidine 5′-monophosphate decarboxylase:: pKa of the C-6 proton of enzyme-bound UMP [J].