ABSTRACT
This chapter begins with the speculation that a nonspecific cellular sensor/switch began its biochemical evolution with condensation of amino acids on primordial clays. It describes that cytochrome P450 systems resemble the primordial peroxidase. The hydrocarbon to be hydroxylated by the cytochrome P450 to a more soluble material for detoxification and excretion is usually hydrophobic, such as an alkane, alkene, aromatic or polycyclic. A corollary to this central theme is that the archetype of this molecular sensor/switch and the metabolic pathways in which it was incorporated evolved and diversified into general cellular energy-generating and defensive pathways. The type-b cytochromes are presented as the modern representative of the candidate for the original cellular sensor/switch. The type-b cytochromes are related to peroxidase and the globlins—hemogloblins and myoglobin. The insoluble cytochrome b's such as NADPH oxidase may be associated with solubilizing and stabilizing subunits or chaperonins as are all cytochrome b's to be transported into cellular membranes.
