In vivo functions of the intra-organellar glutathione peroxidase-type enzymes in African trypanosomes

在非洲锥虫中，氢过氧化物解毒完全依赖于2-Cys-过氧化物氧还蛋白和非硒谷胱甘肽过氧化物酶型（Px）酶，这两种酶都从独特的锥虫硫酮/tryparedoxin系统中获得其还原当量。虽然细胞溶质过氧化物酶已被详细研究，几乎没有什么是已知的Px型酶在不同的亚细胞区室。在这项工作中，我们将调查在体内的线粒体和puereclycosomal Px III的功能。由于在布氏锥虫的哺乳动物血流形式中，该基因的缺失不会导致增殖缺陷，因此我们将敲除具有全功能性补体的前环昆虫形式中的该基因;将在动物模型中研究Px III缺陷型血流寄生虫的毒力。表征可能ER-居民Px IV应该揭示，如果酶是必不可少的，如果它催化脂质氢过氧化物的解毒或可能减少过氧化氢与蛋白质二硫键异构酶作为电子源。后者的反应最近已报告ER-本地化的哺乳动物谷胱甘肽过氧化物酶，并提供了一个全新的功能，这种类型的过氧化物酶。计划中的工作应该为我们提供一个全面的图片，这些巯基过氧化物酶的锥虫的锥虫硫基氧化还原代谢的不同作用。

In African trypanosomes hydroperoxide detoxification relies exclusively on 2-Cys-peroxiredoxins and non-selenium glutathione peroxidase-type (Px) enzymes which both obtain their reducing equivalents from the unique trypanothione/tryparedoxin system. Whereas the cytosolic peroxidases have been studied in detail, nearly nothing is known about the Px-type enzymes in the different subcellular compartments. Within this work we will investigate the in vivo functions of the mitochondrial and putatively glycosomal Px III. Since in the mammalian bloodstream form of Trypanosoma brucei, deletion of the gene did not result in a proliferation defect, we will knock-out the gene in the procyclic insect form which possesses a fully functional mitochondrion; virulence of the Px III-deficient bloodstream parasites will be studied in the animal model. Characterisation of the probably ER-resident Px IV should reveal if the enzyme is essential and if it catalyzes the detoxification of lipid hydroperoxides or may reduce hydrogen peroxide with protein disulfide isomerases as electron source. This latter reaction has recently been reported for ER-localized mammalian glutathione peroxidases and would offer a totally new function of this type of peroxidases. The planned work should provide us with a comprehensive picture of the distinct roles of these thiol peroxidases within the trypanothione-based redox metabolism of trypanosomes.