On the protective mechanism of the thiol-specific antioxidant enzyme against the oxidative damage of biomacromolecules.

摘要: A thiol-specific antioxidant enzyme (TSA), which provides protection against the inactivation of other enzymes by thiol/Fe(III)/oxygen system, was previously isolated and cloned. We investigated mechanism TSA protects biomolecules from oxidative damage caused thiol-containing oxidation system using spin trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Thiyl radicals dithiothreitol (.DTT) were produced horseradish peroxidase/H2O2 under aerobic anaerobic conditions Fe(III)/oxygen system. The formation DMPO-.DTT radical adducts inhibited regardless thiyl radical-generating used. active mutant C170S also quenched signals adduct, whereas inactive C47S did not exert any effect. It found that has a higher rate at initial stage reaction than native enzyme, although failed to remove completely. These results indicate only can catalyze removal radicals, cysteine 47 is required for this activity. In addition, react oxygen generate unidentified thiylperoxy species. Fe.EDTA reacts species reactive abstract hydrogen atom ethanol produce hydroxyethyl radical. This thiyl-oxygen believed be responsible causing deleterious effects on biomolecules. Together, our data catalyzing before they more radicals. However, presently we cannot rule out possibility use as substrates.