RATE-DETERMINING STEPS IN PENICILLOPEPSIN-CATALYZED REACTIONS

被引：2

作者：

CUNNINGHAM, A

HOFMANN, MI

HOFMANN, T

机构：

[1] UNIV TORONTO,DEPT BIOCHEM,KINGS COLL CIRCLE,TORONTO M5S 1A8,ONTARIO,CANADA

[2] UNIV TORONTO,DEPT ZOOL,TORONTO M5S 1A8,ONTARIO,CANADA

来源：

FEBS LETTERS | 1990年 / 276卷 / 1-2期

基金：

英国医学研究理事会;

关键词：

PENICILLOPEPSIN; ASPARTIC PROTEINASE; ENZYME KINETICS; ENZYME MECHANISM;

D O I：

10.1016/0014-5793(90)80522-K

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 hydrolysis of Ac-(Ala)2-Lys-Nph-(Ala)2-amide (II) by penicillopepsin is characterized by a solvent isotope effect of 2.11, whereas the hydrolysis of Ac-Lys-Nph-amide (I) shows no solvent isotope effect. The dependence of the isotope effect on the concentration of D2O in H2O for substrate II is not linear and suggests that two or more protons are involved in its rate-determining step. We propose that for substrate I the rate-determining step is the distortion of the scissile bond towards a tetrahedral configuration, and for substrate II a conformational change induced by the occupation of the S3 pocket in the enzyme.

引用

页码：119 / 122

页数：4