myeloperoxidase (MPO)

Function

• part of host defense system of polymorphonuclear leukocytes
• responsible for microbicidal activity against a wide range of organisms
• in stimulated PMN, MPO catalyzes the production of hypohalous acids, primarily hypochlorous acid in physiologic situations, & other toxic intermediates that greatly enhance PMN microbicidal activity

Donor + H2O2 = oxidized donor + 2 H2O

Cl(-) + H2O2 = HOCl + 2 H2O

Cofactor:

• binds 1 Ca+2 per heterodimer
• binds 1 heme B (iron-protoporphyrin IX) group covalently per heterodimer

Structure

• tetramer of two light chains & two heavy chains
• belongs to the peroxidase family. XPO subfamily

Compartment

lysosome

Alternative splicing

named isoforms=3

Pathology

• defects in MPO are the cause of myeloperoxidase deficiency
• blood levels of myeloperoxidase predictive of adverse coronary outcomes* in patients with chest pain; it is a better predictor than CRP or troponin-T; MPO accumulates in ruptured atheromatous plaques

* myocardial infarction, death

More general terms

• peroxidase
• glycoprotein
• Ca+2 binding protein

Additional terms

• myeloperoxidase deficiency

Database

• UniProt: http://www.uniprot.org/uniprot/P05164.html
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:4353
• OMIM: https://mirror.omim.org/entry/254600
• OMIM: https://mirror.omim.org/entry/606989