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Inhibition of human glutathione S-transferase P1-1 by the flavonoid quercetin

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Author: Zanden, J.J. van · Hamman, O.B. · Iersel, M.L.P.S. van · Boeren, S. · Cnubben, N.H.P. · Lo Bello, M. · Vervoort, J. · Bladeren, P.J. van · Rietjens, I.M.C.M.
Type:article
Date:2003
Source:Chemico-Biological Interactions, 2, 145, 139-148
Identifier: 237083
doi: doi:10.1016/S0009-2797(02)00250-8
Keywords: Biology · Physiological Sciences · Cysteine · Glutathione S-transferase · Inhibition · Quercetin · Quinone · ascorbic acid · cysteine · flavonoid · glutathione · glutathione transferase · isoenzyme · mutant protein · quercetin · article · chemical interaction · concentration response · covalent bond · dimerization · enzyme inhibition · human · incubation time · inhibition kinetics · time · Chromatography, High Pressure Liquid · Dose-Response Relationship, Drug · Glutathione Transferase · Humans · Mass Spectrometry · Molecular Structure · Monophenol Monooxygenase · Mutation · Quercetin

Abstract

In the present study, the inhibition of human glutathione S-transferase P1-1 (GSTP1-1) by the flavonoid quercetin has been investigated. The results show a time- and concentration-dependent inhibition of GSTP1-1 by quercetin. GSTP1-1 activity is completely inhibited upon 1 h incubation with 100 μM quercetin or 2 h incubation with 25 μM quercetin, whereas 1 and 10 μM quercetin inhibit GSTP1-1 activity to a significant extent reaching a maximum of 25 and 42% inhibition respectively after 2 h. Co-incubation with tyrosinase greatly enhances the rate of inactivation, whereas co-incubation with ascorbic acid or glutathione prevents this inhibition. Addition of glutathione upon complete inactivation of GSTP1-1 partially restores the activity. Inhibition studies with the GSTP1-1 mutants C47S, C101S and the double mutant C47S/C101S showed that cysteine 47 is the key residue in the interaction between quercetin and GSTP1-1. HPLC and LC-MS analysis of trypsin digested GSTP1-1 inhibited by quercetin did not show formation of a covalent bond between Cys 47 residue of the peptide fragment 45-54 and quercetin. It was demonstrated that the inability to detect the covalent quercetin-peptide adduct using LC-MS is due to the reversible nature of the adduct-formation in combination with rapid and preferential dimerization of the peptide fragment once liberated from the protein. Nevertheless, the results of the present study indicate that quinone-type oxidation products of quercetin likely act as specific active site inhibitors of GSTP1-1 by binding to cysteine 47. © 2002 Elsevier Science Ireland Ltd. All rights reserved.