Kinetic beta-deuterium isotope effects suggest a covalent mechanism for the protein folding enzyme peptidylprolyl cis/trans-isomerase.
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 beta-deuterium isotope effects. The hydrogen atom at the alpha-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 kH/kD greater than 1. When catalysed by 17 kDa PPIase the same bond rotation is characterized by kH/kD less than 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.
Fischer
G
G
Martin-Luther-Universität Halle, Abteilung Enzymologie, GDR.
Berger
E
E
Bang
H
H
D000591:Amino Acid Isomerases / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D003903:Deuterium / Q000378:metabolism*; D007554:Isotopes; D007672:Kidney Cortex / Q000201:enzymology; D007700:Kinetics; D019696:Peptidylprolyl Isomerase; D013552:Swine
D007554:Isotopes; D003903:Deuterium; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase