Cytochrome P450 IA2 Activity in Man Measured by Caffeine Metabolism: Effect of Smoking, Broccoli and Exercise
Caffeine is sequentially metabolized by cytochrome P450IA2, N-acetyl transferase (NAT) and/or xanthine oxidase (XO). After ingestion of caffeine, equivalent to the content of a cup of coffee, the activity of these three enzymes can be estimated from the ratios of the formed metabolites excreted into the urine (Grant, D.M. et al., 1983; Grant, D.M. et al., 1986; Campbell, M.E. et al., 1987; Figure 1). Cytochrome P450IA2 and NAT are considered the most important enzymes in the metabolic activation of foreign com,pound, such as arylamines, into carcinogens (Butler, M.A. et al., 1989; Hein, D.W., 1988), whereas XO may be important in tissue damage after ischaemia and in relation to infections (Simpson, P.J. et al., 1987; Oda, T. et al., 1989).
KeywordsXanthine Oxidase Metabolic Ratio Metabolite Ratio Xanthine Oxidase Activity Caffeine Metabolism
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