TABLE 5

Relative glucuronidation rates of steroid substrates by human liver microsomes and selected recombinant UGTs The activity of each UGT toward a given aglycone is presented as a ratio of its glucuronidation rate and the respective value of 5α-A glucuronidation.


Number

Substrate

Formation of Steroid Glucuronides Relative to 5α-AG
Human Liver Microsomes
UGT1A3
UGT1A4
UGT2B4
UGT2B7
UGT1A10
1 5β-N 1.42 0.57 0.04 1.23 6.81 0.02
2 5α-A 1.00 1.00 1.00 1.00 1.00 1.00
3 5β-EPIM 0.75 0.03 5.91 2.02 0.02
4 5α-ME 0.54 3.00 0.44 2.70 0.70
5 TES 0.07 0.24 0.01 < 0.01 0.03 0.09
6 5β-MT 0.07 0.08 0.14 0.10 0.18
7 NAN 0.06 0.20 0.03 0.01 < 0.01 0.80
8 5α-N 0.05 0.10 0.01 0.03 0.25
9 5α-1-ME 0.04 0.03 0.17 0.02 0.03 0.90
10 5α-MT 0.04 0.08 0.06 0.09 0.07
11
MT
< 0.01