TABLE 2

Kinetic parameters (mean ± S.D.) for the sulfonation of various xenobiotics by polar bear liver cytosol, listed in order of decreasing enzymatic efficiency

All data fit eq. 1, except for 4′-OH-PCB79 and PCP, which fit eqs. 3 and 2, respectively (see Materials and Methods for equations).

Substrate
Vmax
Km
Vmax/Km
Ki
pmol/min/mg μM μl/min/mg μM
Triclosan 1008 ± 135 11 ± 2 90.8 ± 6.8
4′-OH-PCB79 372 ± 38 123 ± 20 3.1 ± 0.3 217 ± 25a
OHMXC 51.1 ± 7.8 67 ± 4 0.8 ± 0.1
4′-OH-PCB165 8.6 ± 2.0 17 ± 7 0.56 ± 0.17
TCPM 62.0 ± 11.2 144 ± 36 0.44 ± 0.06
4′-OH-PCB159 14.8 ± 2.3 60 ± 21 0.28 ± 0.12
PCP
13.8 ± 1.2
72 ± 14b
0.20 ± 0.05

  • ↵ a Ki values for bears G, K, and X were 240, 220, and 190 μM, respectively. These values were constrained to obtain the best fit for the data.

  • ↵ b S50h; h = 2.0 ± 0.4.