Hydrogen peroxide physiological role

The true physiological role of cytochrome c peroxidase in yeast is yet to be established. It may serve as a part of the systems which prevent intracellular accumulation of harmful hydrogen peroxide. It would be of interest to know if cytochrome c peroxidase is synthesized concurrently with or in competition with the production of other peroxide-decomposing systems such as catalase. Although cytochrome c peroxidase is present in mitochondria of aerobically grown yeast in a concentration comparable to that of cytochrome oxidase (19) and possesses an extremely high molecular activity (fcj = 10 sec ) toward yeast ferrocytochrome c (17), it has not been unequivocally shown that ferrocytochrome c is a true substrate of this enzyme. 

Physiological Function. The mechanism by which L-ascorbic acid benefits an insect is unknown. The vitamin is found in many tissues where it probably plays a variety of roles related to its redox potential. Besides the possible general function of detoxifying superoxide and hydrogen peroxide, L-ascorbic acid may be involved in metabolic processes such as tyrosine metabolism, collagen formation, steroid synthesis, detoxification reactions, phagostimulation, or neuromodulation. At this time one can only speculate about the function of vitamin C in some specific tissues. 

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