Radiation sensitivity of an Escherichia coli mutant lacking NADP(+)-dependent isocitrate dehydrogenase

Ionizing radiation induces the production of reactive oxygen species, which play an important causative role in radiation damage. NADP(+)-dependent is ocitrate dehydrogenase (ICDH) in Escherichia coli produces NADPH, an essent ial reducing equivalent for the antioxidant system. The protective role of ICDH against ionizing radiation in E, coli was investigated in wild-type an d ICDH-deficient strains. Upon exposure to ionizing radiation, the viabilit y was lower and the lipid peroxidation was higher in mutant cells compared to wild-type cells. Activities of key antioxidant enzymes such as superoxid e dismutase, catalase, glutathione reductase, and glucose 6-phosphate dehyd rogenase were decreased by irradiation in both cells. Results suggest that ICDH plays an important role as an antioxidant enzyme in cellular defense a gainst ionizing radiation, (C) 1999 Academic Press.