Page 150 - Veterinary Immunology, 10th Edition

VetBooks.ir Myeloperoxidase then catalyzes the reaction between hydrogen

peroxide and chloride ions to produce hypochlorite:

−
Plasma Cl is used in most inflammatory sites except in milk and
−
saliva, where SCN is also employed. Hypochlorous acid (HOCl) is
the major product of neutrophil oxidative metabolism. Because of
its reactivity, HOCl is rapidly consumed in multiple reactions. As
long as H O is supplied (neutrophils can generate H O for up to 3
2 2 2 2
hours after triggering), myeloperoxidase will generate HOCl. HOCl
kills bacteria by unfolding and aggregating their proteins and
oxidizing their lipids, and it enhances the bactericidal activities of

the lysosomal enzymes. (Remember that HOCl is the active
ingredient of household bleach and is commonly used to prevent
bacterial growth in swimming pools.)
There are quantitative differences in neutrophil activity between
the domestic species, especially in the intensity of the respiratory

burst. For example, sheep neutrophils produce less superoxide than
human or bovine neutrophils. Neutrophils also have safety
mechanisms to detoxify oxidants and minimize collateral damage.

Thus they contain large amounts of glutathione, which reduces the
oxidants. Redox-active metals such as iron can be bound to
lactoferrin to minimize -OH formation, and antioxidants such as
ascorbate and vitamin E interrupt these reactions.
Superoxide, hydrogen peroxide, singlet oxygen, hypohalides and

organic peroxides are collectively known by the term reactive oxygen
species (ROS). These molecules act at the atomic level, binding to
sulfur atoms in the side chains of cysteine and methionine. They

inhibit serine/threonine kinases and phosphatases, many
transcription factors, signal-regulating proteins and ion channels.
They also oxidize bases in DNA and so influence transcription. ROS
activate inflammasomes and promote B and T cell activation.

Lytic Enzymes

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