OSCN- reacts with Cys residues

The reaction of hypothiocyanite (OSCN(-)) with cysteine-derived sulfhydryl groups produces sulfenyl thiocyanates (Cys-S-SCN) which in turn may form disulfides or sulfenic acids (Cys-SOH) that can then be repaired through enzymatic mechanisms (Skaff O et al. 2009; Nagy P et al. 2009; Trujillo M et a. 2015). OSCN(-) is produced by two-electron oxidation of thiocyanate (SCN(-)) in the presence of hydrogen peroxide (H2O2) (Furtmüller PG et al. 2006; Ashby MT 2008). SCN(-) oxidation is catalyzed by defensive human peroxidases, myeloperoxidase (MPO) and lactoperoxidase (LPO), occurring in human secretory mucosa, including the oral cavity, airway, and alimentary tract (Ihalin R et al. 2006; Furtmüller PG et al. 2006; Ashby MT 2008). The OSCN(-) is the conjugate base of hypothiocyanous acid (HOSCN). Both OSCN(-) and HOSCN are potent antimicrobial species that kill invading pathogens. OSCN(-)/HOSCN are thought to oxidize sulphydryls of essential proteins of a microorganism, resulting in an alteration in its cellular functions and thus regulating resident and transient flora in human secretory mucosa as part of innate immunity (Hoogendoorn H et al. 1977; Thomas EL & Aune TM 1978; Mickelson MN 1979; Hawkins CL 2009). OSCN(-)/HOSCN have been viewed as mild oxidants, which are better tolerated by host tissue (Chandler JD et al.2013; Chandler JD & Day BJ 2012). However, HOSCN may target specific thiol-containing cellular proteins resulting n the initiation of significant cellular damage (Barrett TJ & Hawkins CL 2012).

硫氰酸氢根离子（OSCN(-)）与半胱氨酸衍生的硫醇基团反应，生成亚砜硫氰酸酯（Cys-S-SCN），这些亚砜硫氰酸酯进而可能形成二硫键或亚磺酸（Cys-SOH），随后可通过酶促机制进行修复（Skaff O 等人，2009；Nagy P 等人，2009；Trujillo M 等人，2015）。OSCN(-)是在过氧化氢（H2O2）存在下，通过硫氰酸根离子（SCN(-)）的双电子氧化而产生（Furtmüller PG 等人，2006；Ashby MT，2008）。SCN(-)的氧化反应由防御性人过氧化物酶，如髓过氧化物酶（MPO）和乳过氧化物酶（LPO）催化，这些酶存在于人体的分泌性黏膜中，包括口腔、呼吸道和消化系统（Ihalin R 等人，2006；Furtmüller PG 等人，2006；Ashby MT，2008）。OSCN(-)是硫氰酸氢（HOSCN）的共轭碱。OSCN(-)和HOSCN均为强效的抗菌物质，能够杀死入侵的病原体。据信，OSCN(-)/HOSCN能氧化微生物关键蛋白中的硫醇，从而改变其细胞功能，并在人体分泌性黏膜中调节常驻和暂时性菌群，作为先天免疫的一部分（Hoogendoorn H 等人，1977；Thomas EL & Aune TM，1978；Mickelson MN，1979；Hawkins CL，2009）。OSCN(-)/HOSCN被视为温和的氧化剂，对宿主组织耐受性较好（Chandler JD 等人，2013；Chandler JD & Day BJ，2012）。然而，HOSCN可能靶向特定的含硫醇的细胞蛋白，从而启动显著的细胞损伤（Barrett TJ & Hawkins CL，2012）。