SUSCEPTIBILITY OF GLUTATHIONE-PEROXIDASE AND GLUTATHIONE-REDUCTASE TOOXIDATIVE DAMAGE AND THE PROTECTIVE EFFECT OF SPIN-TRAPPING AGENTS

Susceptibility of two key protective enzymes, glutathione peroxidase ( GPX) and glutathione reductase (GR), to oxidative damage and the possi ble protective action of spin traps have been studied. Several oxidizi ng protocols including: (a) Fe(II) or Fe(III)/ascorbate, (b) a singlet oxygen producing system (methylene blue and visible light), (c) ozone , and (d) a hydroxyl radical-generating system (hydrogen peroxide/uv l ight) have been employed. Our results show that both enzymes are susce ptible to oxidative modification and damage as indicated by the loss o f activity and formation of carbonyl groups (in the case of GR). Treat ment of GR with any of the mentioned oxidants resulted in formation of carbonyl groups and inactivation except when treated with iron, where the observed carbonyl formation was not accompanied with significant activity loss. GPX was inactivated to varying degrees when treated wit h the mentioned oxidants, but no carbonyls were detected. Ultraviolet exposure per se resulted in inactivation of both enzymes. Presence of the spin traps N-tert-butyl-alpha-phenylnitrone or 5,5'-dimethyl-1-pyr oline-N-oxide was effective in protecting the enzymes against oxidatio n by uv, hydrogen peroxide/uv, and ozone as determined by the preserva tion of activity and decreased carbonyl content. The degree of protect ion, however, was found to be specific for each enzyme and for the emp loyed oxidizing system. (C) 1944 Academic Press, Inc.