Winterbourn C C, Metodiewa D
Department of Pathology, Christchurch School of Medicine, New Zealand.
Free Radic Biol Med. 1999 Aug;27(3-4):322-8. doi: 10.1016/s0891-5849(99)00051-9.
The reactivities of glutathione, cysteine, cysteamine, penicillamine, N-acetylcysteine, dithiothreitol and captopril with superoxide generated from xanthine oxidase and hypoxanthine, and with reagent hydrogen peroxide, have been investigated. Rates of thiol loss on adding hydrogen peroxide, and superoxide-dependent thiol loss and oxygen uptake were measured. The relative reactivities of the different thiols with both oxidants were inversely related to the pK of the thiol group, such that at pH 7.4, penicillamine was the most reactive. N-acetylcysteine weakly reactive and no reaction was seen with captopril. For hydrogen peroxide, the calculated rate constants for the reaction with the thiolate anion all fell within the range 18-26 M(-1) s(-1). With superoxide, our results are consistent with each thiol reacting via a short chain that consumes oxygen and regenerates superoxide. Only with some of the thiols, was the consumed oxygen recovered as hydrogen peroxide. Reported values for the rate constant for the reaction of thiols with superoxide vary over four orders of magnitude, with the highest being > 10(5) M(-1) s(-1). Due to the complexity of the chain reaction, no study so far has been able to obtain accurate values and we consider the best estimates to be in the 30 to 1000 M(-1) s(-1) range.
研究了谷胱甘肽、半胱氨酸、半胱胺、青霉胺、N-乙酰半胱氨酸、二硫苏糖醇和卡托普利与黄嘌呤氧化酶和次黄嘌呤产生的超氧化物以及与试剂过氧化氢的反应活性。测定了加入过氧化氢时硫醇损失的速率、超氧化物依赖性硫醇损失和氧气摄取量。不同硫醇与两种氧化剂的相对反应活性与硫醇基团的pK呈反比，因此在pH 7.4时，青霉胺反应活性最高。N-乙酰半胱氨酸反应活性较弱，卡托普利未观察到反应。对于过氧化氢，与硫醇阴离子反应的计算速率常数均在18 - 26 M⁻¹ s⁻¹范围内。对于超氧化物，我们的结果表明，每种硫醇通过消耗氧气并再生超氧化物的短链进行反应。只有部分硫醇消耗的氧气以过氧化氢的形式回收。硫醇与超氧化物反应的速率常数报道值相差四个数量级，最高值>10⁵ M⁻¹ s⁻¹。由于链反应的复杂性，迄今为止尚无研究能够获得准确值，我们认为最佳估计值在30至1000 M⁻¹ s⁻¹范围内。
