TABLE 1

Kinetic constants for the inactivation of P450 3A4 by CPE and TFCPE

Inactivation of the BFC O-debenzylation activity or testosterone β-hydroxylation activity of P450 3A4 was measured by incubating P450 3A4 with increasing concentrations of CPE or TFCPE. Aliquots of the sample were removed at different time points and assayed for residual activity as shown in Figs. 2 and 3 for BFC. The kinetic constants were derived from the double reciprocal plots of the rates of inactivation as a function of inactivator concentration. The data show the averages from three different experiments.