TABLE 2

Kinetic parameters determined for DHEA 7β- and 16α-hydroxylation by expressed CYP3A forms

Activities determined for DHEA concentrations of 1 to 200 μM were fit to a one-site Michaelis-Menten equation as described under Materials and Methods. Intrinsic clearance is defined as the quotient of Vmax and apparent Km.


Expressed CYP

DHEA Metabolite

Km

Vmax

Clint
μM nmol/min/nmol
3A4 7β-OH 42.3 17.9 0.423
3A7 7β-OH 23.8 0.298 0.0125
3A5 7β-OH 187 2.45 0.0134
3A4 16α-OH 10.0 4.33 0.433
3A7 16α-OH 12.0 15.8 1.32
3A5
16α-OH
218
0.391
0.0018