The mechanism of microperoxidase-8 (MP-8) mediated O- and N-dealkylation wa
s investigated. In the absence of ascorbate (peroxidase mode), many unident
ified polymeric products are formed and the extent of substrate degradation
correlates (r = 0.94) with the calculated substrate ionization potential,
reflecting the formation of radical intermediates.
In the presence of ascorbate (P450 mode) formation of polymeric products is
largely prevented but, surprisingly, dealkylation is not affected. In addi
tion, aromatic hydroxylation and oxidative dehalogenation is observed. The
results exclude a radical mechanism and indicate the involvement of a (hydr
o)peroxo-iron heme intermediate in P450-type of heteroatom dealkylation.