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Rate‐determining steps in penicillopepsin‐catalysed reactions
Author(s) -
Cunningham Annie,
Hofmann Martin I.,
Hofmann Theo
Publication year - 1990
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(90)80522-k
Subject(s) - chemistry , kinetic isotope effect , amide , scissile bond , substrate (aquarium) , tetrahedral carbonyl addition compound , hydrolysis , solvent , aminolysis , stereochemistry , peptide bond , crystallography , enzyme , organic chemistry , substrate specificity , catalysis , physics , oceanography , deuterium , quantum mechanics , nucleophile , geology
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 D 2 O in H 2 O 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 S 3 pocket in the enzyme.