title: Microbicidal activity of vascular peroxidase 1 in human plasma via generation of hypochlorous acid.
abstract: Members of the heme peroxidase family play an important role in host defense. Myeloperoxidase (MPO) is expressed in phagocytes and is the only animal heme peroxidase previously reported to be capable of using chloride ion as a substrate to form the highly microbicidal species hypochlorous acid (HOCl) at neutral pH. Despite the potent bacterial killing activity of HOCl, individuals who fail to express MPO typically show only a modest increase in some fungal infections. This may point to the existence of redundant host defense mechanisms. Vascular peroxidase 1 (VPO1) is newly discovered member of the heme peroxidase family. VPO1 is expressed in cells of the cardiovascular system and is secreted into the bloodstream. In the present study, we investigate whether VPO1 is capable of generating HOCl and its role in host defense. Like MPO, VPO1 in the presence of H₂O₂ and chloride generates HOCl. VPO1-dependent HOCl generation was demonstrated by chlorination of taurine and tyrosine using mass spectrometry. In addition, the VPO1/H₂O₂/Cl⁻ system can cause the chlorination of monochlorodimedone and the oxidation of 5-thio-2-nitrobenzoic acid. Purified VPO1 and VPO1 in plasma mediate bacterial killing that is dependent on chloride and H₂O₂; killing is inhibited by peroxidase inhibitors and by the H₂O₂ scavenger catalase. In the presence of erythrocytes, bacterial killing by VPO1 is slightly reduced. Thus, VPO1, in addition to MPO, is the second member of the heme peroxidase family capable of generating HOCl under physiological conditions. VPO1 is likely to participate in host defense, with bactericidal activity mediated through the generation of HOCl.
authors.affiliation: Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Zehong
authors.initials: Z
authors.lastname: Cao
authors.forename: D Ray
authors.initials: DR
authors.lastname: Moore
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Jackson
authors.forename: Stephen
authors.initials: S
authors.lastname: Barnes
authors.forename: J David
authors.initials: JD
authors.lastname: Lambeth
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Thannickal
authors.forename: Guangjie
authors.initials: G
authors.lastname: Cheng
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000276:immunology / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D006420:Hemeproteins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D006997:Hypochlorous Acid / Q000276:immunology / Q000378:metabolism*; D013058:Mass Spectrometry; D050296:Microbial Viability / Q000187:drug effects; D010544:Peroxidases / Q000276:immunology / Q000378:metabolism*; D010949:Plasma / Q000201:enzymology*; D013654:Taurine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D000097423:Peroxidasin
chemical_list: D000890:Anti-Infective Agents; D002712:Chlorides; D006420:Hemeproteins; D006861:Hydrogen Peroxide; D006997:Hypochlorous Acid; D010544:Peroxidases; D013654:Taurine; D014443:Tyrosine; C535215:PXDN protein, human; D000097423:Peroxidasin