Meta-Biol

• Pathways

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).