Reactive sulfur species: kinetics and mechanism of the reaction of thiocarbamate-S-oxide with cysteine.
Reactive sulfur species: kinetics and mechanism of the reaction of thiocarbamate-S-oxide with cysteine.
复制标题
DOI：
10.1021/tx800195n
复制
发表时间：
2008-10
影响因子：
4.1
通讯作者：
Xiaoguang Wang;M. Ashby
中科院分区：
文献类型：
--
作者：
Xiaoguang Wang;M. Ashby
次硫氰酸盐(OSCN(-))是一种潜在的抗菌剂，由人的防御性过氧化物酶产生，包括唾液过氧化物酶、乳过氧化物酶、嗜酸性粒细胞过氧化物酶和髓过氧化物酶。OSCN(-)与半胱氨酸衍生的巯基的反应被认为参与了抗菌作用的机制。次硫氰酸盐通过一种未知的机制分解，涉及多个氧化还原和水解步骤，最终生成CN(-)/OCN(-)和SO(3)(2-)/SO(4)(2-)的混合物。直到最近，还没有关于化学级联过程中产生的中间体(S)的化学性质的信息，但我们已经证明OSCN(-)经过水解得到新的化合物硫代氨基甲酸酯-S-氧化物，H(2)NC(=O)SO(-)。在本文中，我们证明了H(2)NC(=O)SO(-)与半胱氨酸(CySH)以类似于OSCN(-)与半胱氨酸反应的两步反应机制：HoZ+CySH->；CySZ+H(2)O和CySZ+CySH->；CySSCy+HZ，其中Z=SCN和SC(=O)NH(2)。本文研究了H(2)、NC(=O)、SO(-)与CySH反应的两步反应动力学和反应机理。
Hypothiocyanite (OSCN(-)) is a putative antimicrobial that is produced by defensive human peroxidases, including salivary peroxidase, lactoperoxidase, eosinophil peroxidase, and myeloperoxidase. The reaction of OSCN(-) with cysteine-derived sulfhydryl groups is believed to be involved in the antimicrobial mechanism of action. Hypothiocyanite decomposes via an unknown mechanism that involves multiple redox and hydrolytic steps to eventually yield mixtures of CN(-)/OCN(-) and SO(3)(2-)/SO(4)(2-). Until recently, no information was available regarding the chemical nature of the intermediate(s) that are produced during the chemical cascade, but we have shown that OSCN(-) undergoes hydrolysis to give the new compound thiocarbamate-S-oxide, H(2)NC(=O)SO(-). In the present paper, we demonstrate that H(2)NC(=O)SO(-) reacts with cysteine (CySH) via a two-step mechanism that is analogous to that of OSCN(-) with cysteine: HOZ + CySH --> CySZ + H(2)O and CySZ + CySH --> CySSCy + HZ, where Z = SCN and SC(=O)NH(2), respectively. The kinetics and mechanism of both steps of the reaction of H(2)NC(=O)SO(-) with CySH have been investigated as a function of pH.