The Urinary Excretion of Amino Acid Conjugates in Free Living Adult Males

occurs predominantly in the liver, is often classified as a two phase process, phase I and phase II (Caldwel, 1982). Phase I metabolism involves the introduction of functional polar groups, whereas phase II metabolism enhances the excretion of the foreign compounds by covalently conjugating endogenous molecules to the metabolites produced in phase I reactions. Often it is the phase II conjugation reactions that are successful in terms of detoxification by terminating the biological activity of the compound by excretion. Of the seven major groups of conjugation reactions listed by Caldwell (Caldwell, 1980), glucuronidation, sulfation, glutathione, and amino acid conjugates are of major concern in humans. This view of our current knowledge of xenobiotic metabolism suggests that a profile of the detoxification capability of the human might be developed by measuring the levels of urinary end products, such as conjugates.