The Enigma of 2-Cys Peroxiredoxins: What Are Their Roles?

Molecular characterization and functional analysis of peroxiredoxin 3 (NdPrx3) from Neocaridina denticulata sinensis

Peroxiredoxins (Prxs) widely exist in organisms and can prevent oxidative damage. Here, the characterization and biological function of NdPrx3 from Neocaridina denticulata sinensis were analyzed. The coding sequence of NdPrx3 consists of 684 bp open reading frame (ORF), encoding 227 amino acids with a predicted molecular weight of 24.7 kDa and theoretical pI 6.49. Multiple sequence alignments showed that the conserved domains of NdPrx3, including catalytic triad, dimer interface, decamer interface, peroxidatic, and resolving cysteines, were similar to those of other organisms. The phylogenetic relationship demonstrated that NdPrx3 clustered in the Prx3 class. The highest relative expression of NdPrx3 mRNA was confirmed in gill among the nine tissues from healthy shrimp. The transcript level of NdPrx3 was significantly upregulated from 0 h to 48 h and decreased in 72 h under copper challenge, indicating that NdPrx3 may play an important role in the copper challenge of N. denticulata sinensis. In addition, NdPrx3 was recombinantly expressed in E. coli and purified to one band on SDS-PAGE. The DNA protection of rNdPrx3 was verified. The enzymatic assay of the recombinant NdPrx3 indicated that it had the oxidoreductase function and was stable at a low temperature (10-30 °C).

Peroxiredoxin, Senescence, and Cancer

Peroxiredoxins are multifunctional enzymes that play a key role in protecting cells from stresses and maintaining the homeostasis of many cellular processes. Peroxiredoxins were firstly identified as antioxidant enzymes that can be found in all living organisms. Later studies demonstrated that peroxiredoxins also act as redox signaling regulators, chaperones, and proinflammatory factors and play important roles in oxidative defense, redox signaling, protein folding, cycle cell progression, DNA integrity, inflammation, and carcinogenesis. The versatility of peroxiredoxins is mainly based on their unique active center cysteine with a wide range of redox states and the ability to switch between low- and high-molecular-weight species for regulating their peroxidase and chaperone activities. Understanding the molecular mechanisms of peroxiredoxin in these processes will allow the development of new approaches to enhance longevity and to treat various cancers. In this article, we briefly review the history of peroxiredoxins, summarize recent advances in our understanding of peroxiredoxins in aging- and cancer-related biological processes, and discuss the future perspectives of using peroxiredoxins in disease diagnostics and treatments.

Hydroperoxide-Reducing Enzymes in the Regulation of Free-Radical Processes

The review presents current concepts of the molecular mechanisms of oxidative stress development and describes main stages of the free-radical reactions in oxidative stress. Endogenous and exogenous factors of the oxidative stress development, including dysfunction of cell oxidoreductase systems, as well as the effects of various external physicochemical factors, are discussed. The review also describes the main components of the antioxidant defense system and stages of its evolution, with a special focus on peroxiredoxins, glutathione peroxidases, and glutathione S-transferases, which share some phylogenetic, structural, and catalytic properties. The substrate specificity, as well as the similarities and differences in the catalytic mechanisms of these enzymes, are discussed in detail. The role of peroxiredoxins, glutathione peroxidases, and glutathione S-transferases in the regulation of hydroperoxide-mediated intracellular and intercellular signaling and interactions of these enzymes with receptors and non-receptor proteins are described. An important contribution of hydroperoxide-reducing enzymes to the antioxidant protection and regulation of such cell processes as growth, differentiation, and apoptosis is demonstrated.