<prompt> Respiratory burst is due to which enzyme -NADPH oxidaseCatalaseSODGlutathione peroxidase  <response>: Ans. is a i.e., NADPH oxidase Respiratory Burst o To deal with microbial infection, phagocytes produce toxic oxygen radical in a process known as a respiratory burst. The generation of reactive oxygen intermediates is due to activation of NADPH oxidaseQ o During phagocytosis, microbial killing is accomplished largely by oxygen-dependent mechanisms, o This oxygen-dependent killing is due to generation of reactive oxygen species reactive oxygen intermediates. o The generation of reactive oxygen intermediates is due to rapid activation of an oxidase-NADPH oxidase, o This NADPH oxidase oxidizes NADPH and in the process, reduces oxygen to superoxide anion O2-. o Superoxide anion is then converted into Hf, by spontaneous dismutation. o H2O2, can be further reduced to the highly reactive hydroxyl radicle OH. o H2O2 generated by NADPH oxidase system is generally not able to efficiently kill microbes itself, o However, the azurophilic granules of neutrophils contain the enzyme myeloperoxidase MPO, which in the presence of a halide such as C1-, convertes H2O2 to hypochlorite HOCl. o Hypochlorite is a potent antimicrobial agent that destroys microbes by halogenation or by oxidation of protein lipids. o The H2O2 - MPO - halide system is the most efficient bactericidal system in neutrophils. 