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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Design of Peptidyl-Inhibitors for Glutathione Transferase (GST)Useful in Targeted Cancer ChemotherapyIrine Axarli 1 , Georgia A. Kotzia 1 , Christos Petrou 2 , Paul Cordopatis 2 ,Nikolaos E. Labrou 1 , and Yannis D. Clonis 11 Laboratory of Enzyme Technology, Department of Agricultural Biotechnology,Agricultural University of Athens, 75 Iera Odos Street, GR-11855, Athens, Greece;2 Laboratory οf Pharmacognosy and Chemistry of Natural Products, Department ofPharmacy, University of Patras, GR- 26500, Patra, GreeceIntroductionGSTs [1-4] have emerged as a promising therapeutic target because specific isozymes areoverexpressed in a wide variety of tumours and may play a role in the aetiology of otherdiseases, including neurodegenerative diseases, multiple sclerosis and asthma. A commonproblem encountered in cancer chemotherapy is the appearance of chemotherapeuticresistant tumour cells. A possible origin for the problem appears to be an increase in theexpression of total GST activity. It is plausible that GSTs serve two distinct roles in thedevelopment of drug resistance via direct detoxification as well as acting as an inhibitor ofthe mitogen-activated protein (MAP) kinase pathway. In addition to glutathioneconjugating activity, GSTs exhibit sulfonamidase activity and catalyze the GSH-mediatedhydrolysis of sulphonamide bonds. Such reactions are of interest as potential tumourdirectedpro-drug activation strategies [3].Results and DiscussionFig. 1. Interaction of sulphanilamide leadligandwith hGSTA1-1 from docking calculations.Side-chains of specific residuescontributing to sulphanilamide binding arepresented as thin stick. The ligand is shownas thick stick.Human GSTA1-1 (hGSTA1-1) was clonedand expressed in E. coli (10-20% of solubleE. coli protein). The enzyme is ahomodimeric protein. Each monomer hastwo domains, an / -domain that includes1- 3 helices and a large α-helical domaincomprising helices 4- 9. The formercontains the GSH-binding site (G-site) ontop of the -domain. A hydrophobic pocket(H-site) lies between the domains in whicha hydrophobic substrate binds and reactswith GSH (Figure 1). The recombinantenzyme was purified to homogeneity in asingle-step by affinity chromatography onimmobilized glutathione. GSTs exhibitsulphonamidase activity and catalyze theGSH-mediated hydrolysis of sulphonamidebonds to form the corresponding amine(Figure 2). In the present work we reportthe design and synthesis of chimaericsulphonamide-derivatives which can beactivated by the model human isoenzymeGSTA1-1 (hGSTA1-1). These chimaeric molecules consist of (i) a bombesin-moiety(Table 1) (analogues [Leu 13 ]-bombesin, [Phe 13 ]-bombesin and [Ser 3 ,Arg 10 ,Phe 13 ]-bombesin) as a structural element determining the drug selectively to tumour cells, able torecognize bombesin receptors present on the tumour cell surface, and (ii) an aromaticsulfonamide moiety. Sulfonamide bombesin analogues were synthesized by Fmoc solidphase methodology [5] utilizing Rink Amide MBHA resin [6] as the solid support.R ONH SOFig. 2. Sulfonamide cleavage by hGSTA1-1.G+ GSH RNH 2 + S+ SO 226