Which of the following helps in generating oxygen burst in the neurophils ?
NADPH oxidase Although oxygen is the lifeline of all cells and tissues, its molecular form i.e., oxygen free radicals (or reactive oxygen intermediate) are devastating for cells. Cells generate energy by reducing molecular oxygen to water. During this process small amounts of paially reduced reactive oxygen forms are produced as a byproduct of respiration. They are called free radicals or reactive oxygen species. Free radicals are chemical species that have single unpaired electron in an outer orbit. This makes them highly reactive. Free radicals are devastating for the cell as they damage lipids, proteins and nucleic acids. Examples of free radical or reactive oxygen species Superoxide 02- Hydroxyl radical OH? Hydrogen peroxide (H202) The noxious effect of free radicals on various cellular material is being utilized by neutrophils to kill bacterias or other microorganisms. Once the neutrophils phagocytize the bacterias there is rapid respiratory burst in the neutrophils which leads to increased oxygen consumption, glycogenolysis and increased glucose oxidation. These reactions lead to rapid burst of superoxide (and other. free radical) production as a by product of the oxidation. This rapid burst in oxidative respiration is made possible by the rapid activation of an enzyme complex, NADPH oxidase, which oxidizes NADPH and in the process reduces oxygen to superoxide anion (024 NADPH oxidase is an enzyme complex that consists of at least seven proteins. The enzyme consists of two complex ? a) Membrane complex b) Cytosolic complex In resting neutrophils various components of this enzyme complex is located in the plasma membrane and cytoplasm. When the neutrophils are activated the enzyme complex shifts to the phagosomal membrane. The H202generated by the NADPH oxidase system is generally not able to efficiently kill microbes by itself However, azurophilic granules of neutrophils release the enzyme myeloperoxidase (MPO) which in presence of halides such as Cl- conves 11202 to HOCL. The latter is a potent antimicrobial agent that destroys microbes by halogenation. The H202 - MPO halide system is the most efficient bactericidal system in neutrophils.
NADPH oxidase
Sod (superoxide dismutase)
Catalase
Glutathione peroxidose