Inactivation and Degradation of CuZn-SOD by Active Oxygen Species in Wheat Chloroplasts Exposed to Photooxidative Stress

Abstract

Changes in CuZn-SOD activity and content in isolated wheat chloroplasts under the light, and the involvement of protease(s) and/or active oxygen species in this process were studied. Both SOD activity and content decayed with exposure time to photooxidative stress. Ascorbate, a H2O2 scavenger, prevented photooxidation-associated inactivation of SOD, while benzoate, a .OH scavenger, prevented SOD degradation. Wheat chloroplasts incubated in the dark did not hydrolyze exogenous or endogenous SOD, either H2O2-pretreated or not. Protease inhibitors did not prevent SOD degradation under photooxidative treatment, suggesting that plastid protease(s) did not participate in this process. Purified chloroplast CuZn-SOD was exposed to H2O2 and O2- or .OH-generating systems. O2- had no effect on either SOD activity or stability (estimated by native PAGE). H2O2 up to 700 microM inhibited SOD in a dose-dependent manner and induced charge/mass changes as seen by native PAGE. .OH also reduced SOD activity by inducing its fragmentation. High levels of active oxygen, as can be generated under strong stress conditions, could directly inactivate and degrade chloroplastic SOD.

Study of destruxin B and tea saponin, their interaction and synergism activities with Bacillus thuringiensis kurstaki against Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)

“…The combination of all biochemicals (DBϩTsϩBt) resulted in suppressed SOD values but did not differ significantly from the control except on day 6 and after 4 days of treatment with CAT. The values of these enzymes may fluctuate as documented by researchers (Casano et al, 1997;Cakmak, 2000) that high lev-426 M. RIZWAN-UL-HAQ et al els of H 2 O 2 inhibit SOD through the formation of excess hydroxyl radicals, whereas the CAT enzyme is sensitive to O 2 . Ϫ and can be inactivated by its increased levels.…”

UVA + B treatment affects antioxidant system and phytochemicals of parsley plant under different concentrations of Zn

“…Reduction in the activity of SOD enzyme as a result of UV-B radiation has been reported for sun flower plant (Costa et al, 2002). It has been proposed that a high amount of H 2 O 2 is able to inhibit Cu-Zn-SOD via the reduction of Cu 2+ to Cu + (Casano et al 1997). Zn is able to facilitate the biosynthesis of antioxidant enzymes (Cakmak, 2000) and its effects on improvement of antioxidant system of plants under various stresses have reported by several authors (Tavallali et al, 2010;Weiasany et al, 2012;Michael and Krishnaswamy, 2014).…”

Paraquat: An Oxidative Stress Inducer

“…OH) are highly reactive compounds that induce protein and pigment degradation, lipid peroxidation, nucleic acid damage, affecting key components of plant cell metabolism that can finally lead to cell death. These deleterious reactions triggered by ROS are known as oxidative stress phenomenon (Casano et al, 1994(Casano et al, , 1997Lascano et al, 1998Lascano et al, , 1999.…”

“…In most plants, CuZn-SOD and Fe-SOD are present in the chloroplasts, CuZn-SOD in the cytosol and Mn-SOD in mitochondria (Casano et al, 1997;Scandalios, 1993). Degradation of H 2 O 2 , in the chloroplasts and in the cytosol is carried out by the ascorbate-glutathione cycle, which involves APX and GR activities (Lascano et al, 1999(Lascano et al, , 2003.…”