Gamain B, Arnaud J, Favier A, Camus D, Dive D, Slomianny C
Institut National de la Santé et de la Recherche Médicale Unité 42, Villeneuve d'Ascq, France.
Free Radic Biol Med. 1996;21(4):559-65. doi: 10.1016/0891-5849(96)00120-7.
Glutathione peroxidase (GPx), a key enzyme involved in the detoxification of many peroxides, has been investigated in two malaria parasite species: P. yoelii in vivo (murine malaria) and P. falciparum in vitro (human malaria). We demonstrate the presence of an endogenous GPx activity in these two Plasmodia species. Enzymatic assays and the use of specific substrates and inhibitors allowed us to determine that the activity is selenium dependent. As this activity was shown to be lower in P. falciparum than in P. yoelii, and selenium levels were found to be low in culture medium and culture red blood cells, we hypothesized that a severe selenium deficiency could be responsible for this difference. After selenium supplementation, with either sodium selenite or selenocystine, we observed an increase in growth of P. falciparum only in with sodium selenite, whereas higher GPx activities were noted in parasites grown in media supplemented with both. An increase in GPx activities was also observed in parasites that had undergone an experimental oxidative stress with TBOOH. As the erythrocyte is unable to synthesize new proteins, these results provide further evidence for the existence of an endogenous parasitic selenium-dependent glutathione peroxidase.
谷胱甘肽过氧化物酶（GPx）是参与多种过氧化物解毒的关键酶，已在两种疟原虫中进行了研究：体内的约氏疟原虫（鼠疟）和体外的恶性疟原虫（人疟）。我们证明了这两种疟原虫物种中存在内源性GPx活性。酶促测定以及使用特定底物和抑制剂使我们能够确定该活性是硒依赖性的。由于该活性在恶性疟原虫中低于约氏疟原虫，并且发现培养基和培养的红细胞中硒水平较低，我们推测严重的硒缺乏可能是造成这种差异的原因。在用亚硒酸钠或硒代胱氨酸补充硒后，我们仅观察到用亚硒酸钠处理时恶性疟原虫的生长增加，而在同时添加这两种物质的培养基中生长的寄生虫中观察到更高的GPx活性。在用叔丁基过氧化氢进行实验性氧化应激处理的寄生虫中也观察到GPx活性增加。由于红细胞无法合成新蛋白质，这些结果为内源性寄生硒依赖性谷胱甘肽过氧化物酶的存在提供了进一步的证据。
