Buthionine sulfoximine is a multitarget inhibitor of trypanothione synthesis in <i>Trypanosoma cruzi</i>

Abstract

Buthionine sulfoximine ( BSO ) induces decreased glutathione (GSH) and trypanothione [T( SH ) 2 ] pools in trypanosomatids, presumably because only gamma‐glutamylcysteine synthetase (γ ECS ) is blocked. However, some BSO effects cannot be explained by exclusive γ ECS inhibition; therefore, its effect on the T( SH ) 2 metabolism pathway in Trypanosoma cruzi was re‐examined. Parasites exposed to BSO did not synthesize T( SH ) 2 even when supplemented with cysteine or GSH, suggesting trypanothione synthetase (TryS) inhibition by BSO . Indeed, recombinant γ ECS and TryS, but not GSH synthetase, were inhibited by BSO and kinetics and docking analyses on a Tc TryS 3D model suggested BSO binding at the GSH site. Furthermore, parasites overexpressing γ ECS and TryS showed ~ 50% decreased activities after BSO treatment. These results indicated that BSO is also an inhibitor of TryS.