Superoxidase dismutase

Figure 15 Structures of type 1 copper protein, Azurin (a) and Type 2 copper protein, Copper, zinc superoxidase dismutase (b). (Reprinted with permission from Ref. 23. 2001 the American Chemical Society)...

Superoxidase dismutase (SOD). This enzyme, which occurs in various body tissues and fluids, including milk, scavenges superoxide radicals (O2) which are powerful pro-oxidants. SOD is discussed more fully in Chapter 8. 

The formation of superoxide is the result of one electron transfer by several coenzymes in ETS, including flavins, flavoproteins, quinones, and iron sulfur proteins. This product has a longer half-life than other intermediates and is toxic to anaerobic bacteria. Peroxidase is formed by two electron transfers and mediated by flavoproteins. Peroxidase is further reduced to the hydroxyl radical with the addition of one electron followed by subsequent reduction to water by the addition of another electron. The oxidative effect of these intermediates can result in the destruction of cells. The aerobic bacteria have enzyme systems such as superoxidase dismutase, peroxidase, and catalase to reduce the toxic levels of these intermediates. 

Varma, S. D., Srivastava, V. K., and Richards, R. D., 1982, Photoperoxidation in lens and cataract formation Preventative role of superoxidase dismutase, catalase and vitamin C, Ophthalmic Res. 14 167-175. 

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