ABSTRACT
The discovery of oxygen radical production by microsomes was made during the same
‘‘gold age’’ of free radical studies in biology (the late 1960s to the beginning of 1970s) as
the discovery of enzymatic production of superoxide, mitochondrial production of reactive
oxygen species, and production of oxygen radicals by phagocytes. Microsomes from animals,
plants, and microorganisms contain the mixed function oxidase system, which consists of
flavoprotein NADPH-cytochrome P-450 reductase and NADH cytochrome b5 reductase.
This system is able to oxidize numerous substrates including drugs, carcinogens, antioxidants,
pesticides, alcohols, steroids, lipid hydroperoxides, etc., and therefore, it is not surprising that
its reactions are mediated by free radicals.
