Regulation of antioxidant nzymes1

0892-6638/92/0006-2675/$01.50. © FASEB 2675 ABSTRACT Free radicals generated by a partial reduction of 02 pose a serious hazard to tissues and vital organs, especially membrane lipids, connective tissues, and the nucleic acids of cells. For protection, enzymes have evolved that specifically attack Of, hydrogen, and organic peroxides, and repair any damage incurred to DNA. With few exceptions, antioxidant enzymes are found in all aerobic and aerotolerant anaerobic organisms. Logic assumes that a basal level of antioxidant enzyme activity is maintained at all times. This may be true. Yet cells must have ways to amplify antioxidant enzyme activity to counter sudden increases in oxygen metabolites. The full details of that regulation are slowly coming to light. Bacteria possess a series of elaborate and interacting genes that can sense specific increases in intracellular H202 and Of. In higher organisms, hormones and metal ion cofactors impose preand posttranslational control over the genetic expression of antioxidant enzymes. Furthermore, aging, cellular differentiation, and organ specificity must also be factored into the final equation in higher organisms. This review will discuss some of the more recent findings relevant to antioxidant enzyme regulation in bacteria and higher organisms.Harris, E. D. Regulation of antioxidant enzymes. FASEB J. 6: 2675-2683; 1992.