Inter(pseudo)halogens with relevance to peroxidase-mediated reactions

In mammals, heme peroxidases are well known to generate oxidized (pseudo)halide products such as hypochlorous acid, hypobromous acid, oxidized iodine species, and hypothiocyanite. In addition, inter(pseudo)halogens are also oxidized (pseudo)halide compounds where two or more different (pseudo)halides are combined within a molecule without participation of other atoms. However, the information of this group of chemicals as potential products of peroxidases is limited and very fragmentary. In this review, we summarize current knowledge about chemical properties of inter(pseudo)halogens, their role as products of peroxidase-mediated conversions, and possible applications of these compounds in antimicrobial defense. The major focus is directed on bromyl chloride, cyanogen halides, and some products derived from interaction of oxidized iodine with thiocyanate.