Tabatabaie T, Floyd R A
Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, Oklahoma City 73104.
Arch Biochem Biophys. 1994 Oct;314(1):112-9. doi: 10.1006/abbi.1994.1418.
Susceptibility of two key protective enzymes, glutathione peroxidase (GPX) and glutathione reductase (GR), to oxidative damage and the possible protective action of spin traps have been studied. Several oxidizing 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 light) have been employed. Our results show that both enzymes are susceptible to oxidative modification and damage as indicated by the loss of activity and formation of carbonyl groups (in the case of GR). Treatment 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 with 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-pyroline-N-oxide was effective in protecting the enzymes against oxidation by uv, hydrogen peroxide/uv, and ozone as determined by the preservation of activity and decreased carbonyl content. The degree of protection, however, was found to be specific for each enzyme and for the employed oxidizing system.
研究了两种关键的保护酶——谷胱甘肽过氧化物酶（GPX）和谷胱甘肽还原酶（GR）对氧化损伤的敏感性以及自旋捕获剂可能的保护作用。采用了几种氧化方案，包括：（a）Fe（II）或Fe（III）/抗坏血酸，（b）单线态氧产生系统（亚甲蓝和可见光），（c）臭氧，以及（d）羟基自由基产生系统（过氧化氢/紫外线）。我们的结果表明，两种酶都易受氧化修饰和损伤，这表现为活性丧失和羰基的形成（就GR而言）。用任何一种上述氧化剂处理GR都会导致羰基形成和失活，但用铁处理时除外，此时观察到的羰基形成并未伴随着显著的活性丧失。用上述氧化剂处理时，GPX会不同程度地失活，但未检测到羰基。紫外线照射本身会导致两种酶失活。通过活性的保留和羰基含量的降低确定，自旋捕获剂N-叔丁基-α-苯基硝酮或5,5'-二甲基-1-吡咯啉-N-氧化物的存在可有效保护酶免受紫外线、过氧化氢/紫外线和臭氧的氧化。然而，发现保护程度因每种酶和所采用的氧化系统而异。
