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 which enzyme is protective?  

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Neutrophils produce reactive oxygen compounds following the phagocytosis of bacteria. Which enzyme protects the body from highly reactive oxygen compounds?
a, cyclooxygenase
b, lipoxygenase
c, myeloperoxidase
d, SOD
e, xanthine oxidase




At first, I thought, Myeloperoxidase found in the lysosomal granules of myeloid cells, particularly macrophages and neutrophils, are responsible for generating potent bacteriocidal activity by the hydrolysis of hydrogen peroxide (produced in the metabolic burst) in the presence of iron containing halide ions.
But Superoxide Dismutase (SOD) is any of a range of metalloenzymes that catalyses the formation of hydrogen peroxide and oxygen from superoxide and thus protects against superoxide induced damage. SOD usually has either iron or manganese as the metal cation in prokaryotes, copper or zinc in eukaryotes.


d, SOD


but SOD still produes toxic free radical H2O2 which is toxic to the tissue? could you guys explain this?


H2O2 is then converted to H2O and 1/2 O2 by catalase


SOD converts superoxide (which cant be metabolized otherwise) to H2O2 that can be metabolized furthur


does all human cells have catalase then? since it's a chain reaction, it's hard to tell which one of them is "protective" cuz them binding together is protective actually.


bluestar, see the option in the question, only SOD out of the options given is active against reactive O2 species


and myeloperoxidase as well,


MPO converts H2O2 to more reactive free radical(HOCl. which is toxic to bacteria)


agre with mash, MPO generates free radicals not detoxifies them


Why do you consider H2O2 a free radical? It doesn't have a misplaced electron.


consider its molecular configuration, things will be clear

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