title: Vascular peroxidase-1 is rapidly secreted, circulates in plasma, and supports dityrosine cross-linking reactions.
abstract: Members of the peroxidase-cyclooxygenase superfamily catalyze biochemical reactions essential to a broad spectrum of biological processes, including host defense, thyroid hormone biosynthesis, and modification of extracellular matrix, as well as contributing to the pathogenesis of chronic inflammatory diseases. We recently identified a novel member of this family, vascular peroxidase-1 (VPO1), that is highly expressed in the human cardiovascular system. Its biosynthesis and enzymatic properties are largely unknown. Here, we report that VPO1 was rapidly and efficiently secreted into the extracellular space when the gene was stably expressed in human embryonic kidney (HEK) cells. Secreted VPO1 is a monomer with complex N-linked oligosaccharides and exhibits peroxidase activity. Biosynthesis of endogenous VPO1 by cultured human umbilical vein endothelial cells (HUVECs) shares features exhibited by heterologous expression of recombinant VPO1 (rVPO1) in HEK cells. The proinflammatory agents lipopolysaccharide and tumor necrosis factor-α induce expression of VPO1 mRNA and protein in HUVECs. Furthermore, murine and bovine sera and human plasma contain enzymatically active VPO1. rVPO1 exhibits spectral and enzymatic properties characteristic of the peroxidase-cyclooxygenase family, except with regard to its heat stability. rVPO1 catalyzes tyrosyl radical formation and promotes dityrosine cross-linking. Taken together, these data demonstrate that VPO1 is a glycosylated heme peroxidase that is actively secreted into circulating plasma by vascular endothelial cells and shares several features with other members of the peroxidase-cyclooxygenase family, including the catalysis of dityrosine formation.
authors.affiliation: Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama School of Medicine, Birmingham, AL 35294, USA. gjcheng@uab.edu
authors.forename: Guangjie
authors.initials: G
authors.lastname: Cheng
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Zehong
authors.initials: Z
authors.lastname: Cao
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Qiu
authors.forename: Sally
authors.initials: S
authors.lastname: McCormick
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Thannickal
authors.forename: William M
authors.initials: WM
authors.lastname: Nauseef
mesh_terms: D000818:Animals; D055162:Biocatalysis; D002417:Cattle; D004795:Enzyme Stability; D015870:Gene Expression / Q000187:drug effects; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000097:blood / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D010957:Plasmids; D011487:Protein Conformation; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood*; D000097423:Peroxidasin
chemical_list: D008070:Lipopolysaccharides; D010544:Peroxidases; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D014443:Tyrosine; C007543:dityrosine; C535215:PXDN protein, human; D000097423:Peroxidasin