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

• Published in: Chemico-biological interactions Vol. 145; no. 2; pp. 139 - 148
• Main Authors: van Zanden, Jelmer J., Ben Hamman, Omar, van Iersel, Marlou L.P.S., Boeren, Sjef, Cnubben, Nicole H.P., Lo Bello, Mario, Vervoort, Jacques, van Bladeren, Peter J., Rietjens, Ivonne M.C.M.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 06-05-2003
• Subjects: active-site; Chromatography, High Pressure Liquid; conjugation; consequences; Cysteine; Dose-Response Relationship, Drug; ethacrynic-acid; Glutathione S-transferase; Glutathione Transferase - antagonists & inhibitors; Glutathione Transferase - genetics; Glutathione Transferase - metabolism; human placenta; Humans; identification; inactivation; Inhibition; Mass Spectrometry; Molecular Structure; Monophenol Monooxygenase - metabolism; Mutation; pi; Quercetin; Quercetin - pharmacokinetics; Quercetin - pharmacology; Quinone; quinone methide; site-directed mutagenesis; Cysteine; Inhibition; Glutathione S-transferase; Quinone; Quercetin
• ISSN: 0009-2797; 1872-7786
• DOI: 10.1016/S0009-2797(02)00250-8

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.