Cytochromes P450 of insects: the tip of the iceberg

The cytochrome P450-dependent monooxygenases are an extremely important met abolic system involved in the metabolism of endogenous compounds and xenobi otics. Collectively, P450 monooxygenases can metabolize numerous substrates and carry out multiple oxidative reactions. The large number: of substrate s metabolized is due to the plethora of P450 isoforms and to the broad subs trate specificity of some isoforms. Monooxygenases of insects have several functional roles, including growth, development, feeding and protection aga inst xenobiotics, including resistance to pesticides and tolerance to plant toxins. This review begins with background information about P450s and the ir evolution, followed by a discussion of the extraordinary diversity of in sect P450s. Given the enormous interest in studying individual P450s, we th en provide a synopsis of the different methods that have been used in their isolation and the substrates that are known to be metabolized. We conclude by summarizing the lessons we have learned from the study of individual in sect P450s, including their roles in insecticide resistance, plant-insect i nteractions and insect physiology. However, these studies are just the 'tip of the iceberg'. Our knowledge continues to expand at a rapid pace, sugges ting that the next decade will outpace the last in, terms of improving our understanding of the cytochromes P450 of insects. (C) 2001 Society of Chemi cal Industry.