Myeloperoxidase

Myeloperoxidase

Peroxidase that plays a central role in the host defense system of polymorphonuclear leukocytes by mediating both (1) formation of neutrophil extracellular trap (NETs) and (2) microbicidal activity16125131,17438335,20974672,20974816,22131345,25066128,28574339,40963017,4978299,6295491. Promotes NET formation by mediating chromatin disassembly: translocates to the nucleus and specifically binds to nucleosomes, both as monomer and homodimer, leading to nucleosome unstacking and initial chromatin decondensation40963017. Homodimers clash with one end of the nucleosomal DNA, leading to DNA unwrapping, initiating complete disassembly of nucleosomes and chromatin transformation into NETs in an ATP-independent manner40963017. NETs, which are mainly composed of DNA fibers and globular proteins, are then extruded into the extracellular space by neutrophils to trap pathogens and release antimicrobial proteins to destroy them40963017. Participates to the microbicidal activity against a wide range of organisms by acting as a peroxidase that catalyzes the formation of oxidants in presence of hydrogen peroxide16125131,17074761,17438335,21880720,22131345,22352991,22902565,24194519,33273015,9359420,9922160. Mediates the formation of hypohalous acids, mainly hypochlorous acid (HOCl) in physiologic situations, that greatly enhance polymorphonuclear leukocyte microbicidal activity16125131,17074761,17438335,19608745,21880720,22902565,24194519,9359420,9922160. In addition to hypochlorous acid, catalyzes formation of hypobromous acid (HOBr), hypoiodous acid (HOI) and hypothiocyanous acid (HOSCN)1318692,16125131,17438335,19608745,6295491,9359420. Also catalyzes oxidation of nitrite into the highly reactive nitrogen dioxide radical10777476,8385644,9450756. Formation of oxidants are widely believed to be responsible for much of the anti-bactericidal activity of neutrophils8385644,9450756. Oxidants, such as hypochlorous acid or nitrogen dioxide radical, can also oxidize amino acid residues on proteins and generate chlorination and nitration post-translational modifications, respectively15314690,15326314,15498770,15574409,16091367,7622459. Chlorination and nitration of the lipid-free form of APOA1 impairs cholesterol transport15326314,15498770,15574409. Superoxides generated by MPO can also promote dioxygenation of tryptophan residues on proteins16091367,40081572. Also able to oxidize melatonin into N1-acetyl-N2-formyl-5-methoxykynuramine either in presence of hydrogen peroxide or superoxide15636586,16148002. Oxidizes urate into 5-hydroxyisourate21266577. Functions as a nitric oxide (NO) oxidase during inflammation, by catalytically consuming NO, impairing NO's ability to maintain vascular tone and function12089442. May also mediate the proteolytic cleavage of alpha-1-microglobulin to form t-alpha-1-microglobulin, which potently inhibits oxidation of low-density lipoprotein particles and limits vascular damage25698971

Light chain of the mature myeloperoxidase

Heavy chain of the mature myeloperoxidase

(Microbial infection) The peroxidase activity is inhibited by S.aureus peroxidase inhibitor SPIN that blocks substrate access to the catalytic heme

Quoted from UniProt’s FUNCTION annotation for P05164 (reviewed). The superscript numbers are UniProt’s own PubMed citations, kept in the sentence and in order, each linking to the paper it names.

What it acts with

STRING’s highest-confidence human functional partners. The combined score mixes several kinds of evidence, so each channel is shown separately — a partner supported by experiment is a different claim from one supported only by text mining, and for a receptor this is where its coupling appears as evidence rather than as assertion.

Where it sits in the cell

• Vesicles
• Nucleoplasmadditional

Human Protein Atlas, by antibody immunofluorescence in cell lines — a different assay from the expression figures below, which are RNA.

UniProt, curated Lysosome · Cytolytic granule · Cytoplasmic vesicle, phagosome · Secreted · Nucleus · Chromosome

Expression by cell type

Single cell type RNA, the 2 highest of those the Human Protein Atlas reports for this gene. Transcript, not protein, and a cell type rather than a tissue.

• Monocyte progenitors2,629 nCPM
• Neutrophil progenitors2,271.8 nCPM

Expression by tissue

The tissues this gene is enriched in, by consensus RNA. A tissue absent from this list is one the Atlas does not call specific for this gene, which is not the same as absent from it.

• bone marrow3,249.5 nTPM