Ohr Protects Corynebacterium Glutamicum Against Organic Hydroperoxide Induced Oxidative Stress

Normal aerobic process will produce Reactive Oxygen Species(ROS), and when cells of antioxidant defense was breached, oxidative stress, cells from square one also to oxidation state. To preclude the adverse effects and maintain the homeostasis, bacteria have evolved complex systems for sensing, protection, and regulation against organic peroxide toxicity and repair damage caused by ROS,including the enzyme and the none-enzyme. The none-enzyme contains the vitamin C or E and the Low molecular weight(LMW) thiols such as the glutathione(GSH) and the Mycothiol(MSH). The enzyme contains glutathione peroxidase(Gpx), superoxidase dismutase(SOD), thioredoxin(Trx) and so on. The coorparation of veriouse enzymes can remove the ROS and repaire the oxdative damage.Ohr, a bacterial protein encoded by the ohr(Organic Hydroperoxide Resistance) gene which can effectively remove ROS in vivo, it is crucial for optimal resistance to organic hydroperoxide. In this study, we demonstrated that the Cys-based, thiol-dependent Ohr of Corynebacterium glutamicum contributes to the decomposition of organic hydroperoxide more efficiently than hydrogen peroxide. Regeneration of the peroxidase activity of oxidized Ohr in C. glutamicum was mainly supported by using lipoylated proteins(LpdA and Lpd/SucB) as the electron donor. What’s more,the classical Trx/TrxR system also can work weakly, however, the MSH/Mrx/Mtr cannot play a part at all. The Ohr can effectively decompose organic hydroperoxide at least 10,000 times than the peroxide. All the Ohr contain two conservered domain, one of which in contained by VCP motif and make the Ohr is a thiol dependent protein. Replacement of either of the two Cys residues of Ohr by Ser residues resulted in drastic loss of activity. Resistance of the Δohr mutant to organic hydroperoxide was significantly decreased while the accumulation of reactive oxygen species(ROS) in vivo was notably increased, resulting in markedly protein carbonylation. Resistance to hydrogen peroxide also decreased but the protein carbonylation was not much increased. Takentogether, these results unequivocally demonstrated that Ohr is vital for C. glutamicum resistance to organic hydroperoxides.