RESUMO
The trans-sialidase protein expressed by Trypanosoma cruzi is an important enzyme in the life cycle of this human pathogenic parasite and is considered a promising target for the development of new drug treatments against Chagas' disease. Here we describe α-amino phosphonates as a novel class of inhibitor of T. cruzi trans-sialidase. Molecular modelling studies were initially used to predict the active-site binding affinities for a series of amino phosphonates, which were subsequently synthesised and their IC50s determined in vitro. The measured inhibitory activities show some correlation with the predictions from molecular modelling, with 1-napthyl derivatives found to be the most potent inhibitors having IC50s in the low micromolar range. Interestingly, kinetic analysis of the mode of inhibition demonstrated that the α-aminophosphonates tested here operate in a non-competitive manner.
Assuntos
Doença de Chagas/tratamento farmacológico , Glicoproteínas/antagonistas & inibidores , Neuraminidase/antagonistas & inibidores , Organofosfonatos/química , Organofosfonatos/farmacologia , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Trypanosoma cruzi/enzimologia , Aminação , Doença de Chagas/parasitologia , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Glicoproteínas/química , Glicoproteínas/metabolismo , Humanos , Simulação de Acoplamento Molecular , Neuraminidase/química , Neuraminidase/metabolismo , Trypanosoma cruzi/efeitos dos fármacosRESUMO
Sialidases are a superfamily of sialic-acid-releasing enzymes that are of significant interest due to their implication as virulence factors in the pathogenesis of a number of diseases. However, extensive studies of viral and microbial sialidases have failed to provide a comprehensive picture of their mechanistic properties, in part because the structures of competent enzyme-substrate complexes and reaction intermediates have never been described. Here we report these structures for the Trypanosoma cruzi trans-sialidase (TcTS), showing that catalysis by sialidases occurs via a similar mechanism to that of other retaining glycosidases, but with some intriguing differences that may have evolved in response to the substrate structure.