Regulation of antioxidant enzymes ¹

Abstract

Free radicals generated by a partial reduction of O2 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 O2-, 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 H2O2 and O2-. In higher organisms, hormones and metal ion cofactors impose pre- and 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.

Transcription and activity of antioxidant enzymes after ionizing irradiation in radiation-resistant and radiation-sensitive mice

“…The posttranscriptional effects, the presence of preformed AOEs or conformational changes by irradiation or its products, generated could have led to increased AOE activity (33). In eukaryotic cells, MnSOD, an SOD isoenzyme, is preformed and stored as a precursor (34).…”

Cellular Oxidative Processes in Relation to Renal Disease

“…It is reinforced by plasma and intracellular ascorbate [15]. There is back-up by the antioxidant enzymes SOD, catalase and glutathione peroxidase [16, 17]. The heat shock proteins often act as SODs [18].…”

Thermosensitive phenotype of transgenic mice overproducing human glutathione peroxidases.

“…and enzymes that are able to eliminate oxygen radicals (1). There are three major antioxidant enzymes, superoxide dismutase (SOD), catalase, and GSH peroxidase (GP) (2). In normal conditions, there is a steady-state balance in production of ROS and cellular antioxidant systems and in activities of different antioxidant enzymes.…”