A Second Class of Peroxidases Linked to the Trypanothione Metabolism

摘要: Abstract Trypanosoma brucei, the causative agent of African sleeping sickness, has three nearly identical genes encoding cysteine homologues classical selenocysteine-containing glutathione peroxidases. The proteins are expressed in mammalian and insect stages parasite. One genes, which contains a mitochondrial as well glycosomal targeting signal been overexpressed. recombinant T. brucei peroxidase high preference for trypanothione/tryparedoxin couple electron donor reduction different hydroperoxides but accepts alsoT. thioredoxin. apparent rate constantsk 2′ regeneration reduced enzyme 2 × 105 m −1s−1 with tryparedoxin 5 103 −1 s−1 No saturation kinetics was observed rate-limiting step overall reaction is hydroperoxide. With glutathione, marginal activity enzymes becomes limiting k value 3 s−1. bruceiperoxidase, contrast to related cruzienzyme, also hydrogen peroxide substrate. catalytic efficiency studied here comparable that peroxiredoxin-like peroxidases, shows trypanosomes possess two distinct systems both dependent on unique dithiol trypanothione.