Glutathione S-transferase phenotypes in relation to genetic variation and fruit and vegetable consumption in an endoscopy-based population
Tijhuis, M.J. ; Visker, M.H.P.W. ; Aarts, J.M.M.J.G. ; Peters, W.H.M. ; Roelofs, H.M.J. ; Camp, E.B.G. op den; Rietjens, I.M.C.M. ; Boerboom, A.M.J.F. ; Nagengast, F.M. ; Kok, F.J. ; Kampman, E. - \ 2007
Carcinogenesis 28 (2007)4. - ISSN 0143-3334 - p. 848 - 857.
brussels-sprouts - aldehyde dehydrogenase - cruciferous vegetables - colorectal-cancer - colon tissue - polymorphisms - expression - alpha - risk - pi
High glutathione S-transferase (GST) activity may contribute to colorectal cancer prevention. Functional polymorphisms are known in the GSTM1, GSTT1, GSTA1 and GSTP1 genes. The influence of these GST polymorphisms and recent fruit and vegetable consumption on GST levels and activity has not been investigated simultaneously in a human population. Also, it is not clear if blood GST activity reflects rectal GST activity. Therefore, we determined GST polymorphisms in 94 patients scheduled for sigmoidoscopy. Rectal GST isoenzyme levels (GSTM1, GSTM2, GSTT1, GSTA and GSTP1) were measured by quantitative Western blotting, and rectal and white blood cell total GST activities were measured spectrophotometrically using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate. Vegetable and fruit consumption was assessed by dietary record. As expected, the GSTM1 and GSTT1 deletion polymorphisms, and the GSTA1 g.-69C>T polymorphism significantly affected the respective isoenzyme levels. Also, rectal GST isoenzyme levels differed between those with and without recent consumption of Alliaceae, Cucurbitaceae, Apiaceae and citrus fruit. Rectal GST activity, however, was not clearly influenced by fruit and vegetable consumption. It was most significantly determined by the GSTP1 c.313A>G polymorphism; compared to the 313AA genotypes, the 313AG and 313GG genotypes showed 36 and 67 nmol/min.mg protein (p
Inhibition of human glutathione S-transferase P1-1 by the flavonoid quercetin
Zanden, J.J. van; Hamman, O. Ben; Iersel, M.L. van; Boeren, J.A. ; Cnubben, N.H.P. ; Bello, M. Lo; Vervoort, J.J.M. ; Bladeren, P.J. van; Rietjens, I.M.C.M. - \ 2003
Chemico-Biological Interactions 145 (2003)2. - ISSN 0009-2797 - p. 139 - 148.
site-directed mutagenesis - human placenta - quinone methide - ethacrynic-acid - active-site - pi - identification - consequences - inactivation - conjugation
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 I h incubation with 100 muM quercetin or 2 h incubation with 25 muM quercetin, whereas 1 and 10 muM 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 LGMS 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 LGMS 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. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.