Table 1

Glucuronidation of endobiotics catalyzed by stably expressed human UGT1A8 and 1A10

SubstrateGlucuronide Formation
UGT1A8UGT1A10
pmol/min/mg protein
Estrogens
 Estrone79ND
 2-Hydroxyestrone27723
 4-Hydroxyestrone118349
 Diethylstilbestrol166ND
 17α-Ethynyl estradiol160ND
Androgens
 AndrosteroneNDND
 Testosterone20ND
 Dihydrotestosterone8136
 Epitestosterone12ND
Progestins
 PregnenoloneNDND
 17α-hydroxyprogesteroneNDND
Fatty acids (0.5 mM)
 Butyric acid (n = 4)NDND
 Caproic acid (n = 6)NDND
 Caprylic acid (n = 8)7ND
 Decanoic acid (n = 10)19ND
 Dedecanoic acid (n = 12)12ND
 Tetradecanoicacid (n = 14)NDND
Bile acids (0.1 mM)
 Lithocholic acid11ND
 5β-etianic acid9ND
 Hyocholic acid39ND
 Hyodeoxycholic acid18ND
Retinoids
 All-trans retinoic acid1-a 35ND
 5,6 epoxy retinoic acid1-a 36ND
 4-Hydroxyretinoic acid1-a 67ND
 4-Hydroxyretinoic acid  methylesterNDND

Assays were performed using pH 7.4 Tris buffer at 37°C for 1.0 h and membrane preparations of HK293 cells expressing UGT1A8 or UGT1A10. The concentration of UDP-glucuronic acid was 2.0 mM and the aglycone concentrations were 0.1 mM or as otherwise indicated. Values represent the average enzymatic rates from two different experiments.

  • ND, not detected (limit of detection is 2.0 pmol/min/mg protein).

  • 1-a Carboxyl-linked glucuronides.