PTP1b is a protein tyrosine phosphatase involved in the inactivation of insulin receptor. Since inhibition of PTP1b may prolong the action of the receptor, PTP1b has become a drug target for the treatment of type II diabetes. In the present study, prediction of inhibition using docking analysis targeted specifically to the active or allosteric site was performed on 87 compounds structurally belonging to 10 different groups. Two groups, consisting of 15 thiomorpholine and 10 thiazolyl derivatives exhibiting the best prediction results, were selected for in vitro evaluation. All thiomorpholines showed inhibitory action (with IC50 = 4-45 μΜ, Ki = 2-23 μM), while only three thiazolyl derivatives showed low inhibition (best IC50 = 18 μΜ, Ki = 9 μΜ). However, free binding energy (E) was in accordance with the IC50 values only for some compounds. Docking analysis targeted to the whole enzyme revealed that the compounds exhibiting IC50 values higher than expected could bind to other peripheral sites with lower free energy, Eo, than when bound to the active/allosteric site. A prediction factor, E- (ΣEo × 0.16), which takes into account lower energy binding to peripheral sites, was proposed and was found to correlate well with the IC50 values following an asymmetrical sigmoidal equation with r2 = 0.9692.
Keywords: PTP1b inhibitors; active site; allosteric site; competitive inhibitors; diabetes, selectivity, TC-PTP; docking analysis; docking box; thiazoles; thiomorpholines; uncompetitive inhibitors.