SUBSTITUENT EFFECTS ON AN ANTIBODY-CATALYZED HYDROLYSIS OF PHENYL-ESTERS - FURTHER EVIDENCE FOR AN ACYL-ANTIBODY INTERMEDIATE

被引:61
作者
GIBBS, RA
BENKOVIC, PA
JANDA, KD
LERNER, RA
BENKOVIC, SJ
机构
[1] PENN STATE UNIV, DEPT CHEM, 152 DAVEY LAB, UNIV PK, PA 16802 USA
[2] SCRIPPS RES INST, DEPT MOLEC BIOL, LA JOLLA, CA 92037 USA
[3] Scripps Res Inst, DEPT CHEM, LA JOLLA, CA 92037 USA
关键词
D O I
10.1021/ja00035a057
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The hydrolysis of a series of para-substituted phenyl esters (2 and 6a-d) by the monoclonal catalytic antibody NPN43C9 has been investigated. The apparent pK(a) observed in the k(cat)/K(m)-pH profiles shifts from 8.9 (p-nitrophenyl ester) up to a maximum of 9.5 (p-methylphenyl ester). A correlation of the antibody-catalyzed rates of hydrolysis of the esters versus the sigma-parameter affords a rho-value of 2.3, indicative of a hydrolytic mechanism proceeding via the attack of a neutral nitrogen nucleophile and contrasting with the low rho-value expected for general base catalyzed hydrolysis. There was an inverse solvent deuterium isotope effect on the antibody-catalyzed hydrolysis of the p-chlorophenyl ester at pH > 10. These observations are consistent with our previous proposal (Benkovic, et al. Science 1990, 250, 1135) that this antibody employs a multistep kinetic pathway which involves the formation of a covalent acyl-antibody intermediate.
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页码:3528 / 3534
页数:7
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