Instituto de Agrobiotecnología del Litoral, UNL-CONICET, 3000 Santa Fe, Argentina.
Free Radic Biol Med. 2011 Jan 1;50(1):37-46. doi: 10.1016/j.freeradbiomed.2010.10.695. Epub 2010 Oct 20.
Methionine is an amino acid susceptible to being oxidized to methionine sulfoxide (MetSO). The reduction of MetSO to methionine is catalyzed by methionine sulfoxide reductase (MSR), an enzyme present in almost all organisms. In trypanosomatids, the study of antioxidant systems has been mainly focused on the involvement of trypanothione, a specific redox component in these organisms. However, no information is available concerning their mechanisms for repairing oxidized proteins, which would be relevant for the survival of these pathogens in the various stages of their life cycle. We report the molecular cloning of three genes encoding a putative A-type MSR in trypanosomatids. The genes were expressed in Escherichia coli, and the corresponding recombinant proteins were purified and functionally characterized. The enzymes were specific for L-Met(S)SO reduction, using Trypanosoma cruzi tryparedoxin I as the reducing substrate. Each enzyme migrated in electrophoresis with a particular profile reflecting the differences they exhibit in superficial charge. The in vivo presence of the enzymes was evidenced by immunological detection in replicative stages of T. cruzi and Trypanosoma brucei. The results support the occurrence of a metabolic pathway in Trypanosoma spp. involved in the critical function of repairing oxidized macromolecules.
蛋氨酸是一种易被氧化为蛋氨酸亚砜（MetSO）的氨基酸。MetSO 还原为蛋氨酸是由蛋氨酸亚砜还原酶（MSR）催化的，该酶几乎存在于所有生物体中。在原生动物中，抗氧化系统的研究主要集中在三肽巯基化合物（trypanothione）上，三肽巯基化合物是这些生物体中一种特殊的氧化还原成分。然而，关于它们修复氧化蛋白质的机制的信息尚不清楚，这对于这些病原体在其生命周期的各个阶段的存活是相关的。我们报告了在原生动物中编码一种假定的 A 型 MSR 的三个基因的分子克隆。这些基因在大肠杆菌中表达，并对相应的重组蛋白进行了纯化和功能表征。这些酶特异性地还原 L-Met（S）SO，使用克氏锥虫的 tryparedoxin I 作为还原底物。每种酶在电泳中的迁移模式都具有特定的特征，反映了它们在表面电荷上的差异。在克氏锥虫和布氏锥虫的复制阶段通过免疫检测证明了这些酶的存在。这些结果支持了在锥虫属中存在一条代谢途径，该途径涉及修复氧化大分子的关键功能。
