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Kinetic β‐deuterium isotope effects suggest a covalent mechanism for the protein folding enzyme peptidylprolyl cis/trans ‐isomerase
Author(s) -
Fischer Gunter,
Berger Edith,
Bang Holger
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80735-5
Subject(s) - chemistry , kinetic isotope effect , covalent bond , isomerase , moiety , deuterium , stereochemistry , residue (chemistry) , catalysis , reaction mechanism , enzyme , organic chemistry , physics , quantum mechanics
The cis/trans interconversion of Glt‐Ala‐Ala‐Pro‐Phe‐4‐nitroanilide and Glt‐Ala‐Gly‐Pro‐Phe‐4‐nitroanilide was studied both enzymatically and nonenzymatically by measuring kinetic β‐deuterium isotope effects. The hydrogen atom at the α‐carbon atom of the Xaa residue within the Xaa‐Pro moiety was substituted by deuterium. In the nonenzymatic case the transition state of rotation is reflected by k H / k D > 1. When catalysed by 17 kDa PPIase the same bond rotation is characterized by k H / k D < 1. This suggests a covalent mechanism of catalysis which involves an approximately tetravalent carbon of the prolyl imidic bond for the transition state of reaction.