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.
Keywords: N-acyl hydrazone; allozyme; benzophenone; enzyme cloning; enzyme inhibition; enzyme kinetics; human glutathione transferase; isoenzyme; ketoxime; protein structure comparative analysis.
© 2015 John Wiley & Sons A/S.