Cytochrome P450 in Humans

Abstract

More than half the described species of eukaryotic organisms living on our planet are insects, and it is generally believed that a vast majority of insect species are still unknown. Among the known insect species are our best friends (pollinators of our crops) and our worst enemies (vectors of disease and avid consumers of our food). It is the chemical warfare against the latter that provided the framework for most of the early studies on insect cytochrome P450. The metabolism of insecticides, its inhibition by synergists such as piperonyl butoxide, and the resistance of insect pests to insecticides are only the most obvious reasons to study insect cytochrome P450. Insects are excellent model systems in which to study the induction of cytochrome P450 by dietary chemicals, or the molecular genetics of cytochrome P450. However, the study of cytochrome P450 has often been hampered by the small size of insects and the difficulty in obtaining enough tissue. Purification and reconstitution studies have been particularly difficulty (Hodgson 1985). Nonetheless, large numbers of insects obtained at low cost can sometimes compensate for small size, and the use of radiolabeled substrates has allowed enzymological studies of cytochrome P450 from tiny endocrine glands such as the corpora allata or the pro thoracic glands. This review is necessarily selective and will survey the known insect cytochromes P450 as well as some aspects of cytochrome P450 function in insects.