Włodek Lidia
Institute of Medical Biochemistry, Collegium Medicum, Jagiellonian University, Kraków, Poland.
Pol J Pharmacol. 2002 May-Jun;54(3):215-23.
Biothiols are extraordinarily efficient antioxidants protecting the cells against consequences of damage induced by free radicals, due to their ability to react with the latter. In such antioxidant reactions, thiols undergo one-electron oxidation with the formation of thiyl radicals. For this reason, attention has been focused mostly on antioxidant properties of thiols. Considerably less attention has been paid to thiyl radicals (RS*) formed simultaneously in these reactions. However, protective and repairing efficacy of thiols depends not only on their capacity to detoxify free radicals but also on chemical character and reactivity of the formed thiyl radical. Furthermore, quick and efficient removal of RS radical leads to a disturbance in balanced state of antioxidant reaction, which effectively increases repairing capacity. Dangerous thiyl radicals, which can cause peroxidative injury, should immediately undergo regenerative reduction to thiols. Under physiological conditions, thiyl radicals can react with thiolate anion yielding disulfide radical anion (RSSR)-* as an intermediate and finally disulfides and superoxide radical anion (O2-*), which is next inactivated in the reaction catalyzed by superoxide dismutase (SOD). Thiyl radicals can also be reduced to thiols by reacting with ascorbate with the formation of low-activity ascorbyl radical, that subsequently enters disproportiation reaction.
生物硫醇是极其有效的抗氧化剂，由于它们能够与自由基反应，从而保护细胞免受自由基诱导损伤的后果。在这种抗氧化反应中，硫醇经历单电子氧化形成硫自由基。因此，人们大多关注硫醇的抗氧化特性。而对这些反应中同时形成的硫自由基（RS*）的关注则少得多。然而，硫醇的保护和修复功效不仅取决于它们清除自由基的能力，还取决于所形成硫自由基的化学性质和反应活性。此外，快速有效地清除RS自由基会导致抗氧化反应平衡状态的紊乱，从而有效提高修复能力。可能导致过氧化损伤的危险硫自由基应立即进行再生还原为硫醇。在生理条件下，硫自由基可与硫醇盐阴离子反应生成二硫自由基阴离子（RSSR）-作为中间体，最终生成二硫化物和超氧自由基阴离子（O2-），后者在超氧化物歧化酶（SOD）催化的反应中被灭活。硫自由基还可与抗坏血酸反应还原为硫醇，同时形成低活性的抗坏血酸自由基，随后该自由基进入歧化反应。
