Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, 11400 Montevideo, Uruguay.
Free Radic Biol Med. 2011 Jan 1;50(1):196-205. doi: 10.1016/j.freeradbiomed.2010.10.705. Epub 2010 Oct 26.
Hydrogen sulfide (H(2)S) is an endogenously generated gas that can also be administered exogenously. It modulates physiological functions and has reported cytoprotective effects. To evaluate a possible antioxidant role, we investigated the reactivity of hydrogen sulfide with several one- and two-electron oxidants. The rate constant of the direct reaction with peroxynitrite was (4.8±1.4)×10(3)M(-1) s(-1) (pH 7.4, 37°C). At low hydrogen sulfide concentrations, oxidation by peroxynitrite led to oxygen consumption, consistent with a one-electron oxidation that initiated a radical chain reaction. Accordingly, pulse radiolysis studies indicated that hydrogen sulfide reacted with nitrogen dioxide at (3.0±0.3)×10(6)M(-1) s(-1) at pH 6 and (1.2±0.1)×10(7)M(-1) s(-1) at pH 7.5 (25°C). The reactions of hydrogen sulfide with hydrogen peroxide, hypochlorite, and taurine chloramine had rate constants of 0.73±0.03, (8±3)×10(7), and 303±27M(-1) s(-1), respectively (pH 7.4, 37°C). The reactivity of hydrogen sulfide was compared to that of low-molecular-weight thiols such as cysteine and glutathione. Considering the low tissue concentrations of endogenous hydrogen sulfide, direct reactions with oxidants probably cannot completely account for its protective effects.
硫化氢（H₂S）是一种内源性气体，也可以外源性给予。它调节生理功能，并具有报道的细胞保护作用。为了评估其可能的抗氧化作用，我们研究了硫化氢与几种单电子和双电子氧化剂的反应性。与过氧亚硝酸反应的速率常数为（4.8±1.4）×10³ M⁻¹ s⁻¹（pH 7.4，37°C）。在低硫化氢浓度下，过氧亚硝酸氧化导致耗氧量，与引发自由基链式反应的单电子氧化一致。因此，脉冲辐射研究表明，硫化氢在 pH 6 时与二氧化氮以（3.0±0.3）×10⁶ M⁻¹ s⁻¹的速率反应，在 pH 7.5 时以（1.2±0.1）×10⁷ M⁻¹ s⁻¹的速率反应（25°C）。硫化氢与过氧化氢、次氯酸盐和牛磺酸氯胺的反应速率常数分别为 0.73±0.03、（8±3）×10⁷和 303±27M⁻¹ s⁻¹（pH 7.4，37°C）。与低分子量巯基化合物如半胱氨酸和谷胱甘肽相比，硫化氢的反应性。考虑到内源性硫化氢的组织浓度较低，与氧化剂的直接反应可能不能完全解释其保护作用。
