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Abiotic Stress-Mediated Oxidative Damage in Plants
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Ruchi Rai, Shilpi Singh, Shweta Rai, Alka Shankar, Antra Chatterjee, L.C. Rai
Glutathione participates in detoxification either directly by interacting with ROS and methylglyoxal or by operating as a cofactor for various enzymes. The reduced and oxidized forms of glutathione (GSH and GSSG) act in concert with other redox-active compounds, e.g., NADPH, to regulate and maintain cellular redox status (Jones et al., 2011). MG detoxification is primarily carried out by the ubiquitous glyoxalase system located in cytoplasm, mitochondria and nucleus. The glyoxalase system comprises two enzymes, glyoxalase I and II, both of which act coordinately on MG and convert it into nontoxic lactic acid using GSH as a cofactor (Racker, 1951; Thornalley, 1990). Glyoxalase I used hemiacetal as a substrate, which is formed by spontaneous reaction of MG and GSH and conversion into S-lactoylglutathione (SLG), which was further hydrolyzed by glyoxalase II into nontoxic lactic acid and regenerate GSH (Racker, 1951; Crook and Law 1952). Methylglyoxal first spontaneously reacts with glutathione to form a hemithioacetal derivative which is then converted to S-lactoylglutathione by the enzyme glyoxalase I:
A comparative study on subacute toxicity of arsenic trioxide and dimethylarsinic acid on antioxidant status in Crandell Rees feline kidney (CRFK), human hepatocellular carcinoma (PLC/PRF/5), and epithelioma papulosum cyprini (EPC) cell lines
Published in Journal of Toxicology and Environmental Health, Part A, 2018
Antonia Concetta Elia, Gabriele Magara, Claudio Caruso, Loretta Masoero, Marino Prearo, Paola Arsieni, Barbara Caldaroni, Ambrosius Josef Martin Dörr, Melissa Scoparo, Stefania Salvati, Paola Brizio, Stefania Squadrone, Maria Cesarina Abete
The detoxification route of the glyoxalase system is accomplished by sequential mechanism of two enzymes. First, GI acts upon the equilibrium adduct of MG or other toxic 2-ketoaldehydes, and GSH catalyzing the formation of the thioester SLG, and then GII catalyzes hydrolysis of thioester to regenerate GSH liberating D-lactate. Norton et al. (1993) postulated factors related to the function(s) of the glyoxalase system, including protection against α-chetoaldehyde toxicity, cell growth regulation, glycolytic bypass, and involvement in microtubule assembly. Both GI and GII activities showed marked reduction predominantly in mammalian (CRFK) and human (PLC/PRF/5) cell lines treated with AsIII. The lowest GI activity suggests diminished ability to inactivate reactive molecules formed during oxidative stress such as α-chetoaldehydes and epoxides, and mainly MG is transformed into the corresponding α-dihydroxyl acid. The lower GI activity may be linked to a lower MG concentration in cells, most likely due to inhibition of glycolytic enzymes with a subsequent decrease of triosephosphate production as the main source of MG. The potential for pharmacological use of α-chetoaldehydes as cytostatic is however limited by the extreme efficiency of glyoxalases in inactivation of such compounds. The use of glyoxalase inhibitors mechanically boosts the efficiency of MG, which demonstrates higher toxicity in tumor than in healthy cells (Chyan et al. 1995; Elia et al. 1995; Norton et al. 1993; Thornalley 1993). Specific GI inhibitors were used as possible inducers of apoptosis and consequently cell death. Arsenite may potentiate the efficacy of toxic α-chetoaldehydes in both CRFK and PLC/PRF/5 cell lines. Reduction of GII activity follows that of GI in the same cells. It is conceivable that a similar response should occur for every cell line since both enzymes work jointly to detoxify ketohaldeydes. Conversely, DMA did not produce the same effect on glyoxalases in EPC, as the level of GI in the treated groups remained unchanged, while the GII activity showed a late fall. Therefore, if the glyoxalase system in cells is weakened, α-chetoaldehydes and mainly MG may produce irreversible damage to protein structures (Thornalley 1993).