PDF(Pubmed)
Abstract：
Peroxiredoxins (Prxs) and glutathione peroxidases (GPxs) are the main enzymes of the thiol-dependent antioxidant systems responsible for reducing the H2O2 produced via aerobic metabolism or parasitic organisms by the host organism. These antioxidant systems maintain a proper redox state in cells. The cysticerci of Taenia crassiceps tolerate millimolar concentrations of this oxidant. To understand the role played by Prxs in this cestode, two genes for Prxs, identified in the genome of Taenia solium (TsPrx1 and TsPrx3), were cloned. The sequence of the proteins suggests that both isoforms belong to the class of typical Prxs 2-Cys. In addition, TsPrx3 harbors a mitochondrial localization signal peptide and two motifs (-GGLG- and -YP-) associated with overoxidation. Our kinetic characterization assigns them as thioredoxin peroxidases (TPxs). While TsPrx1 and TsPrx3 exhibit the same catalytic efficiency, thioredoxin-glutathione reductase from T. crassiceps (TcTGR) was five and eight times higher. Additionally, the latter demonstrated a lower affinity (>30-fold) for H2O2 in comparison with TsPrx1 and TsPrx3. The TcTGR contains a Sec residue in its C-terminal, which confers additional peroxidase activity. The aforementioned aspect implies that TsPrx1 and TsPrx3 are catalytically active at low H2O2 concentrations, and the TcTGR acts at high H2O2 concentrations. These results may explain why the T. crassiceps cysticerci can tolerate high H2O2 concentrations.
摘要：
过氧化物酶（Prxs）和谷胱甘肽过氧化物酶（GPxs）是硫醇依赖性抗氧化系统的主要酶，负责减少宿主生物通过有氧代谢或寄生生物产生的H2O2。这些抗氧化剂系统在细胞中维持适当的氧化还原状态。the虫的囊尾蚴能耐受这种氧化剂的毫摩尔浓度。要了解Prxs在此节食中所起的作用，Prxs的两个基因,在猪带虫（TsPrx1和TsPrx3）的基因组中鉴定，被克隆。蛋白质的序列表明两种同种型都属于典型的Prxs2-Cys类别。此外,TsPrx3具有一个线粒体定位信号肽和两个与过度氧化相关的基序(-GGLG-和-YP-)。我们的动力学表征将它们指定为硫氧还蛋白过氧化物酶（TPxs）。虽然TsPrx1和TsPrx3表现出相同的催化效率，来自T.crassiceps的硫氧还蛋白-谷胱甘肽还原酶（TcTGR）分别高出五倍和八倍。此外,与TsPrx1和TsPrx3相比，后者对H2O2的亲和力较低（>30倍）。TcTGR在其C端含有Sec残基，这赋予了额外的过氧化物酶活性。上述方面意味着TsPrx1和TsPrx3在低H2O2浓度下具有催化活性，并且TcTGR在高H2O2浓度下起作用。这些结果可以解释为什么囊尾股虫可以耐受高H2O2浓度。
