| Abstract
| - Trypanothione reductase is a flavoenzyme unique to trypanosomatid parasites. Here we showthat unsaturated Mannich bases irreversibly inactivate trypanothione reductase from Trypanosoma cruzi, the causative agent of Chagas' disease. The inhibitory potency of the compoundsstrongly increased upon storage of the DMSO stock solutions. HPLC, NMR, and massspectrometry data of potential intermediates revealed a divinyl ketone as the active compoundinactivating the enzyme. ESI- and MALDI-TOF mass spectrometry of trypanothione reductasemodified by the Mannich base or the divinyl ketone showed specific alkylation of the activesite Cys52 by a 5-(2‘chlorophenyl)-3-oxo-4-pentenyl substituent. The reaction mechanism andthe site of alkylation differ from those in Plasmodium falciparum thioredoxin reductase wherethe C-terminal redox active dithiol is modified. After deamination, unsaturated Mannich basesare highly reactive in polycondensation with trypanothione. Interaction of these compoundswith both trypanothione and trypanothione reductase could account for their potent trypanocidaleffect against Trypanosoma brucei.
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