PubMed · 14020721
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J CHEYMOL, M ADOLPHE, F HEITZ. [Catalase and ionizing radiations].. https://pubmed.ncbi.nlm.nih.gov/14020721/
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Changes in catalase (CAT) activity and in CAT isoform pattern and expression were investigated in developing sunflower (Helianthus annuus L.) seeds during desiccation on the mother plant and after artificial drying on the flowerheads. Seeds regularly desiccated during their development on the mother plant and reached mass maturity at c. 42 d after flowering (DAF). Freshly harvested seeds did not germinate at any stage of development because they were dormant, but their dormancy was broken after 5-6 months of dry storage. Immature seeds were desiccation-tolerant at 24 DAF since they were able to germinate fully after artificial drying on the flowerheads followed by dry storage. CAT activity increased in non-dehydrated seeds during their development, reaching a maximum a little after seed mass maturity and after artificial drying in immature seeds. This stimulation of CAT activity by natural and artificial drying was related to changes in CAT isoform pattern. Of the four constitutive CAT subunits, that of 59 kDa was always present, but dehydration induced the synthesis of a 55 kDa subunit. This synthesis of the CAT 55 kDa subunit resulted from an activation of the CATA1 gene, suggesting that the regulation of catalase activity and synthesis by drying occurred at the transcriptional level. The increase in CAT activity induced by seed drying was associated with a decrease in hydrogen peroxide level and in lipid peroxidation. These results suggest that CAT plays a role during seed desiccation by preventing dehydration-related oxidative damage and that H(2)O(2) may play a role in the regulation of CAT gene expression and the transduction pathway of the dehydration signal.
PprI, a newly identified gene switch responsible for extreme radioresistance of Deinococcus radiodurans, plays a central regulatory role in multiple DNA damage repair and protection pathways in response to radiation stress [Biochem. Biophy. Res. Commun. 306 (2003) 354]. To evaluate whether PprI also functions in the radioresistance in other organisms, D. radiodurans PprI protein (Deira-PprI) was expressed in Escherichia coli. The complemented E. coli strain showed an increase of approximately 1.6-fold radioresistance with a high dose of gamma irradiation. Immunoblotting assays showed that the expression of Deira-PprI in E. coli resulted in a significant increase in RecA protein expression following high dose ionizing radiation. The expression of Deira-PprI protein also significantly enhanced the scavenging ability of free radicals by inducing the enzymatic activity of KatG. These results indicate that exogenous expression of Deira-PprI promotes DNA repair and protection pathways and enhances the radioresistance of E. coli.
Methylglyoxal is an endogenous metabolic by-product of glycolysis and has genotoxic effects. Previous studies suggested that the reaction of methylglyoxal with amino acid leads to the production of free radicals. In this study, oxidative damage of DNA by the reaction of methylglyoxal with amino acid was investigated. When plasmid DNA was incubated with methylglyoxal and lysine, DNA strand was cleaved. Cu(2+) enhanced DNA strand breakage induced by the reaction of methylglyoxal with lysine. The formation of superoxide anion was detected during the glycation reaction of methylglyoxal with lysine. Radical scavengers, catalase, and copper chelators inhibited the DNA breakage. The deoxyribose assay showed that hydroxyl radicals were generated during the reaction of methylglyoxal with lysine in the presence of Cu(2+). The generation of hydroxyl radicals was inhibited by radical scavenger, catalase, and copper chelator. These results suggest that superoxide anion and H2O2 may generate from the glycation reaction of methylglyoxal with lysine and then Cu(2+) likely participates in a Fenton's type reaction to produce hydroxyl radicals, which may cause DNA cleavage. This mechanism may be linked to several diverse biological processes including mutagenesis, aging, carcinogenesis, and diabetic complications.