Mutual Modulation of the Activities of Human CYP2D6 and Four UGTs during the Metabolism of Propranolol

Abstract

Cytochromes P450 (CYP) and UDP-glucuronosyltransferases (UGT) are two enzyme families that play an important role in drug metabolism, catalyzing either the functionalization or glucuronidation of xenobiotics. However, their mutual interactions are poorly understood. In this study, the functional interactions of human CYP2D6 with four human UGTs (UGT1A7, UGT1A8, UGT1A9, and UGT2A1) were investigated using our previously established co-expression model system in the fission yeast Schizosaccharomyces pombe. The substrate employed was propranolol because it is well metabolized by CYP2D6. Moreover, the CYP2D6 metabolite 4-hydroxypropranolol is a known substrate for the four UGTs included in this study. Co-expression of either UGT1A7, UGT1A8, or UGT1A9 was found to increase the activity of CYP2D6 by a factor of 3.3, 2.1 or 2.8, respectively, for the conversion of propranolol to 4-hydroxypropranolol. In contrast, UGT2A1 co-expression did not change CYP2D6 activity. On the other hand, the activities of all four UGTs were completely suppressed by co-expression of CYP2D6. This data corroborates our previous report that CYP2D6 is involved in functional CYP-UGT interactions and suggest that such interactions can contribute to both adverse drug reactions and changes in drug efficacy.

Glucuronidation Pathways of 5- and 7-Hydroxypropranolol: Determination of Glucuronide Structures and Enzyme Selectivity

“…Subsequently, the washed cell pellets (referred to as enzyme bags), were resuspended in 200 µL of phosphate-buffered saline (PBS) containing 50% glycerol (v/v). Finally, the enzyme bag samples were flash frozen by liquid nitrogen and stored at −80 • C. The feasibility of utilizing preserved enzyme bags was previously demonstrated [43]. All enzyme bags used in this investigation were frozen for less than three months, which is a suitable storage duration with acceptable activity loss [43].…”

“…Finally, the enzyme bag samples were flash frozen by liquid nitrogen and stored at −80 • C. The feasibility of utilizing preserved enzyme bags was previously demonstrated [43]. All enzyme bags used in this investigation were frozen for less than three months, which is a suitable storage duration with acceptable activity loss [43]. For the investigation of glucuronidation the frozen enzyme bags were thawed on ice and washed twice with NH 4 HCO 3 buffer to eliminate glycerol.…”