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Thromboxane synthase (TXAS) is a P450 epoxygenase that synthesizes thromboxane A2 (TXA2), a potent mediator of platelet aggregation, vasoconstriction and bronchoconstriction. This enzyme plays an important role in several human diseases, including myocardial infarction, stroke, septic shock, asthma and cancer. Despite of the increasing interest on developing TXAS inhibitors, the structure and activity of TXAS are still not totally elucidated. In this study, we used a comparative molecular modeling approach to construct a reliable model of TXAS and analyze its interactions with Dazoxiben and Ozagrel, two competitive inhibitors. Our results were compatible with experimental published data, showing feasible cation-π interaction between the iron atom of the heme group of TXAS and the basic nitrogen atom of the imidazolyl group of those inhibitors. In the absence of the experimental structure of thromboxane synthase, this freely available model may be useful for designing new antiplatelet drugs for diseases related with TXA2.

Recently the literature described the binding of Haptoglobin (HP) with ecotin, a fold-specific serine-proteases inhibitor with an anticoagulant profile and produced by Escherichia coli. In this work, we used some in silico and in vitro techniques to evaluate HP 3D-fold and its interaction with wild-type ecotin and two variants. Our data showed HP models conserved trypsin fold, in agreement to the in vitro immunological recognition of HP by trypsin antibodies. The analysis of the three ecotin-HP complexes using the mutants RR and TSRR/R besides the wild type revealed several hydrogen bonds between HP and ecotin secondary site. These data are in agreement with the in vitro PAGE assays that showed the HP-RR complex in native gel conditions. Interestingly, the ternary complex interactions varied depending on the inhibitor structure and site-directed mutation. The interaction of HP with TSRR/R involved new residues compared to wild type, which infers a binding energy increase caused by the mutation.