Redox regulation mechanisms involving

Iron-sulfur centers can participate in regulation mechanisms either directly, when they control the activity of an enzyme, or at a more integrated level, when they modulate the expression of some genes. The regulation mechanisms that have been elucidated so far involve either a change in the redox state or the interconversion of iron—sulfur centers. 

Apart from being a cofactor of prolyl and lysyl hydroxylase, ascorbate affects the hydroxylation of procollagen at various levels of regulation. It activates a silent form of prolyl hydroxylase (Mussini et al., 1961 Stassen et al, 1973 Hayaishi et al, 1975 Cardinale et al, 1975) and may also increase the enzyme levels by transcriptional activation and translational events (Qian et al, 1993). Interestingly, all these regulatory interventions appear to be linked to the redox properties, i.e., the prooxidant potential of ascorbate. The activation of the inactive form of prolyl hydroxylase is reversed by dithiothreitol (Hayaishi et al, 1975) and the induction of its biosynthesis appears to be mediated by the superoxide ion, which activates an epigenetic control mechanism involving poly ADP-ribose the induction of prolyl hydroxylase by ascorbate is prevented by both addition of superoxide dismutase and inhibition of poly ADP-ribose synthetase (Qian et al, 1993). 

Palozza, P., Serini, S., Torsello, A. et al. 2002b. Regulation of cell cycle progression and apoptosis by beta-carotene in undifferentiated and differentiated HL-60 leukemia cells possible involvement of a redox mechanism. Int J Cancer 97 593-600. 

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