TABLE 2

Kinetic parameters for nicotine 5′ oxidation by P450s 2A enzymes The enzyme assay conditions and the quantitation of products from nicotine 5′-oxidation are described under Materials and Methods. The concentrations of nicotine used for P450 2A3 and P450 2A5 were 1.0, 2.5, 5, 10, 25, 50, and 100 μM. For P450 2A6, two additional concentrations were used: 250 and 500 μM. For P450 2A4, the nicotine concentrations were 10, 25, 50, 100, 250, 500, and 750 μM. Two independent experiments were carried out for each enzyme, and for each experiment duplicate reactions were carried out for each nicotine concentration. Kinetic and statistical analyses were done using the EZ-Fit 5 Kinetics program. Values reported are ±S.E.