= Myeloperoxidase
<Myeloperoxidase> is an <enzyme> that can use <hydrogen peroxide> to oxidize <chloride>, forming <hypochlorous acid>. The enzyme occurs in <neutrophils> and other immune cells, where its oxidant chemistry contributes to antimicrobial activity. One balanced representation of the reaction is:
$$
\mathrm{Cl^-+H_2O_2+H^+\longrightarrow HClO+H_2O}.
$$
The equation identifies consumed reactants and product; the enzyme itself is regenerated during catalysis.<Myeloperoxidase in IUBMB Enzyme Nomenclature>[EC 1.11.2.2, reaction and biological localization]{ref}
A protein's catalytic reaction does not exhaust its possible biological roles. A 2010 study found that <myeloperoxidase> enhanced <chromatin> decondensation together with <neutrophil elastase>, with the enhancement independent of myeloperoxidase's enzymatic activity in the tested system.<Neutrophil elastase and myeloperoxidase regulate the formation of neutrophil extracellular traps by Venizelos Papayannopoulos and others>[Abstract and Fig. 1H, cooperative effect on isolated nuclei]{ref}
This provides a useful experimental distinction: removing a protein and selectively disabling one catalytic activity need not have identical consequences. To assign a phenotype to oxidant production, an experiment must test that chemistry rather than infer it solely from the presence or absence of <myeloperoxidase>.
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