TABLE 4

Kinetic characteristics of TST biotransformation in vitro by HLMs, rCYP3A4, and rCYP3A5, and IC50 values for ketoconazole Results are expressed as mean ± S.E.



6β-HST

HLMs (n = 4)
rCYP3A4
rCYP3A5
V max a 5.4 ± 1.6 3.6 1.6
S50 (μ M) 52 ± 4 24.4 69.4
Vmax/S50b 101 ± 23 147 23
Hill coefficient (a) 1.37 ± 0.08 1.17 1.26
IC50 for ketoconazole (μ M)
0.044 ± 0.005
0.045
0.26
  • For clearance (Vmax/S50 ratio), units are μl/min/mg protein for HLMs and μl/min/pmol P450 for rCYP3A4 and rCYP3A5.

  • a Units are nmol/min/mg protein for HLMs and nmol/min/pmol P450 for rCYP3A4 and rCYP3A5.