Conjugation Mechanisms of Xenobiotic Metabolism: Mammalian Aspects

Living organisms of all types exist in a chemical environment, made up of nutrients (macronutrients, micronutrients and trace elements) and anutrients or xenobiotics. These latter comprise those compounds from which organisms are (virtually) unable to utilize for energy-yielding metabolism, and may be broadly divided into two classes, natural and synthetic. Living organisms may be exposed to xenobiotics (a) deliberately, due to their use as drugs, pesticides, herbicides etc., (b) coincidentally in the diet, most notably in the consumption of plant foods by animals of all types, or (c) accidentally, from industrial, agricultural or other sources. It is the purpose of this review to consider the fates of such xenobiotics in living organisms, as an introduction to the topic of this Symposium volume, concentrating in particular upon the metabolic conjugation reactions as they occur in mammals. When a xenobiotic enters a living organism, it may undergo one or more of a