Table 1

Testosterone hydroxylase assays of CYP3A4 and CYP3A43

Reconstitution ConditionsTestosterone 6β-OH
CYP3A4CYP3A43
nmol/min/nmol
HEPES buffer (pH 7.6)1-a
 1:2:01-b plus 0.02% Na cholate, 15 mM MgCl2, 0.1 mM EDTA14.80.2
 1:2:2 plus 0.02% Na cholate, 15 mM MgCl2, 0.1 mM EDTA44.40.3
KPO4 buffer (pH 7.4)1-c
 1:4:0 plus 0.04% CHAPS13.20.2
 1:4:1 plus 0.04% CHAPS10.20.3
 1:4:2 plus 0.04% CHAPS10.60.3

In the assays listed, the concentration of testosterone was 200 μM and a 1:1:1 mix of DOPC/DLPC/phosphatidylserine was included. The values reported represent the average of two assays performed in duplicate.

    • 1-aUeng et al. (1997).

    • 1-b  1:2:0 refers to the molar ratio of P450 to rat NADPH-P450 reductase to cytochrome b5.

    • 1-cImaoka et al. (1992).