ABSTRACT
One cannot but fail to be impressed and intrigued by the range of substrates successfully oxidised by the cytochromes P450 [1]. These enzymes, present in all aerobic organisms, oxidise intractable substrates, often of limited solubility in aqueous media. In humans, their oxidative talents are used to transform, for example, aromatic hydrocarbons but therein lies the paradox: in doing so, it is thought that they convert a harmful material into a potent carcinogen as in the transformation of benzo[a]pyrene to benzo[a]pyrene 7,8 diol-9,10-epoxide [2]. This marked ability to catalyse difficult oxidations renders cytochromes P450 invaluable for all organisms in taking care of either noxious materials or accessing recalcitrant sources of energy. There is another paradox in this story: to generate a sufficiently powerful oxidant, dioxygen or, effectively, its complex with the cytochrome, must be reduced. That is, the peroxide formed generates a species that is a sufficiently powerful oxidant and, combined with the ability of the enzyme to arrange the substrate in a kinetically advantageous position, leads to the transformation of essentially all materials. One can state, with some confidence, that the advent of genetically engineered forms of the enzyme renders few compounds safe from attack.
