H2O2 degradation by catalase is without any energy. but in ascorbate cycle to H2O2 degeneration why need electron? why do not use catalase enzyme?
The glutathione-ascorbate cycle is a pathway to detoxify H2O2 produced as a waste product in metabolism. The cycle involves the antioxidant metabolites: ascorbate, glutathione and NADPH and the enzymes linking these metabolites. This cycle takes place in cell comparments where there is no catalase.
The complete reaction catalysed by catalase is a dismutation.
It is a two substrate reaction where both substrates are the same molecule.
one H2O2 is oxidized to H2O
the second one is reduced to O2
The catalytic mechanism is Redox catalysis. In Heme peroxidases, the first half of the reaction the H2O2 forms iron(III)-peroxide and the peroxide is reduced to iron(IV)-hydroxide + one hydroxyl ion.
In the second half a second peroxide molecule binds to the iron(IV)-peroxide and is oxidized to H3O+ and iron(III)-O2 complex.
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