title: Isoenzyme- and allozyme-specific inhibitors: 2,2'-dihydroxybenzophenones and their carbonyl N-analogues that discriminate between human glutathione transferase A1-1 and P1-1 allozymes.
abstract: The selectivity of certain benzophenones and their carbonyl N-analogues was investigated towards the human GSTP1-1 allozymes A, B and C involved in MDR. The allozymes were purified from extracts derived from E. coli harbouring the plasmids pEXP5-CT/TOPO-TA-hGSTP1*A, pOXO4-hGSTP1*B or pOXO4-hGSTP1*C. Compound screening with each allozyme activity indicated three compounds with appreciable inhibitory potencies, 12 and 13 with P1-1A 62% and 67%, 11 and 12 with P1-1C 51% and 70%, whereas that of 15 fell behind with P1-1B (41%). These findings were confirmed by IC50 values (74-125 μm). Enzyme inhibition kinetics, aided by molecular modelling and docking, revealed that there is competition with the substrate CDNB for the same binding site on the allozyme (Ki(13/A)  = 63.6 ± 3.0 μm, Ki(15/B)  = 198.6 ± 14.3 μm, and Ki(11/C)  = 16.5 ± 2.7 μm). These data were brought into context by an in silico structural comparative analysis of the targeted proteins. Although the screened compounds showed moderate inhibitory potency against hGSTP1-1, remarkably, some of them demonstrated absolute isoenzyme and/or allozyme selectivity.
authors.affiliation: Laboratory of Enzyme Technology, Department of Biotechnology, Agricultural University of Athens, Athens, Greece.
authors.forename: Foteini M
authors.initials: FM
authors.lastname: Pouliou
authors.affiliation: Laboratory of Genetics, Department of Biotechnology, Agricultural University of Athens, Athens, Greece.
authors.forename: Trias N
authors.initials: TN
authors.lastname: Thireou
authors.affiliation: Laboratory of Genetics, Department of Biotechnology, Agricultural University of Athens, Athens, Greece.
authors.forename: Elias E
authors.initials: EE
authors.lastname: Eliopoulos
authors.affiliation: Laboratory of Biochemistry, Hellenic Pasteur Institute, Athens, Greece.
authors.forename: Petros G
authors.initials: PG
authors.lastname: Tsoungas
authors.affiliation: Laboratory of Enzyme Technology, Department of Biotechnology, Agricultural University of Athens, Athens, Greece.
authors.forename: Nikolaos E
authors.initials: NE
authors.lastname: Labrou
authors.affiliation: Laboratory of Enzyme Technology, Department of Biotechnology, Agricultural University of Athens, Athens, Greece.
authors.forename: Yannis D
authors.initials: YD
authors.lastname: Clonis
mesh_terms: D001577:Benzophenones / Q000737:chemistry* / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D051549:Glutathione S-Transferase pi / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D062105:Molecular Docking Simulation
chemical_list: D001577:Benzophenones; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; C119995:glutathione S-transferase alpha; C121479:2,4-dihydroxybenzophenone
keywords: N-acyl hydrazone; allozyme; benzophenone; enzyme cloning; enzyme inhibition; enzyme kinetics; human glutathione transferase; isoenzyme; ketoxime; protein structure comparative analysis