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.
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