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Antioxidants, nature and chemistry
Submitted by Dr. Tamer Fouad, M.D.
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Antioxidants are substances that
protect other chemicals of the body from damaging oxidation
reactions |
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Glutathione peroxidase
enzyme
The glutathione
redox cycle is a central mechanism for reduction of intracellular hydroperoxides.
(Fig.5).
Source and Nature:
It is a tetrameric
protein 85,000-D. it has 4 atoms of selenium (Se) bound as seleno-cysteine
moieties that confers the catalytic activity. One of the essential requirements
is glutathione as a cosubstrate.
Glutathione peroxidase reduces H2O2
to H2O by oxidizing glutathione (GSH) (Equation A). Rereduction of
the oxidized form of glutathione (GSSG) is then catalysed by glutathione
reductase (Equation B). These enzymes also require trace metal cofactors for
maximal efficiency, including selenium for glutathione peroxidase; copper, zinc,
or manganese for SOD; and iron for catalase (Halliwell,
1995).
H2O2
+ 2 GSH ?
GSSG + 2 H2O (equation A)
GSSG
+ NADPH + H+ ?
2 GSH + NADP+ (equation B)
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