Myeloperoxidase (MPO) is a highly cationic
glycosolated hemoprotein that has a molecular weight
of 144kD. The hemoprotein consists of two dimers
linked via a disulfide bridge. Each dimmer is
composed of a heavy (53kD) and light (15kD) subunit.
Each heavy chain contains an independently acting
protoporphyrin group containing a central iron
(1-5). MPO is present in the azurophilic
granules of polymorphonuclear leukocytes (PMNs) and
is unique to neutrophils and monocytes. However,
monocytes contain only one third of the MPO found in
PMN’s. MPO utilizes H202 produced by the neutrophils
to oxidize a varity of aromatic compounds to give
substrate radicals for bactericidal activity (4
review). This enzyme is unique however in that
it can oxidize chloride ions to produce a strong
nonradical oxidant,HOCl. HOCl is the most powerfull
bactericidal produced by neutrophils (4 review).
Excessive production of these radicals can cause
oxidative stress leading to oxidative tissue injury.