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The chemical modification of human liver UDP‐glucuronosyltransferase UGT1*6 reveals the involvement of a carboxyl group in catalysis
Author(s) -
Eric Battaglia,
Claire Senay,
Sylvie FournelGigleux,
R. Herber,
Gérard Siest,
Jacques Magdalou
Publication year - 1994
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(94)00453-6
Subject(s) - chemistry , glucuronidation , reagent , glucuronic acid , catalysis , carbodiimide , kinetics , sulfonate , residue (chemistry) , biochemistry , stereochemistry , organic chemistry , medicinal chemistry , enzyme , microsome , polysaccharide , physics , quantum mechanics , sodium
The treatment of UDP‐glucuronosyltransferase UGT1*6 stably expressed in V79 cells with three car☐yl‐specific reagents, dicyclohexylcarbodiimide, 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide and N ‐ethyl‐5‐phenylisoxazolium‐3′‐sulfonate (Woodward's reagent K), resulted in a fast, dose‐dependent decrease of the 4‐methylumbelliferone glucuronidation. The inactivation reactions followed pseudo‐first order kinetics. The p K a of the modified residue was close to 5.0. A partial protection against inactivation by Woodward's reagent was observed at pH 7.4 in the presence of UDP‐glucuronic acid, UDP, and, to a lesser extent, in the presence of 4‐methylumbelliferone. Dicyclohexylcarbodiimide significantly decreased the V max , without affecting the apparent K m towards UDP‐glucuronic acid and 4‐methylumbelliferone. The results support the involvement of a car☐yl group in the catalytic process.