Eosinophil peroxidase

Eosinophil peroxidase is a haloperoxidase enzyme that in humans is encoded by the EPX gene. The enzyme is a heterodimeric 71-77 kD peroxidase consisting of a heavier glycosylated chain and a lighter nonglycosylated chain. This enzyme prefers bromide over chloride as a substrate, converting it to toxic hypobromite.

Function

In the presence of H₂O₂ formed by the eosinophil, and either chloride or bromide ions, eosinophil peroxidase provides a potent mechanism by which eosinophils kill multicellular parasites (such as, for example, the nematode worms involved in filariasis); and also certain bacteria (such as tuberculosis bacteria). Eosinophil peroxidase is a haloperoxidase that preferentially uses bromide over chloride for this purpose, generating hypobromite (hypobromous acid). The enzyme is also capable of oxidizing thiocyanate (SCN-) and uses it as a co-substrate, with optimal concentrations occurring at about normal plasma levels.

Eosinophil peroxidase is also partly responsible for tissue remodeling.

Role in pathology

The oxidizing compounds produced by eosinophil peroxidase have been implicated in the inflammatory pathology of several disease states, including asthma.<ref...
Read More