Fig. 7.

Residue 57 contributes to the differential formation of M1 by CYP3A4 and CYP3A5. Decreased M1 formation by the CYP3A5 L57F mutant and increased M1 formation by the CYP3A4 F57L mutant relative to that by wild-type CYP3A5 and CYP3A4, respectively. Protein expression of wild-type (WT) CYP3A4 and the F57L mutant is shown above the right panel and expression of CYP3A5 L57F is shown in Fig. 6A. Metabolite formation was normalized to protein expression as measured using immunoblotting. **, P < 0.01; ***, P < 0.001, compared with wild-type.