Glucuronidation of opioids catalyzed by expressed human UGT1A3
| Substrate | Glucuronide Formation |
|---|---|
| pmol/min/mg of protein | |
| Morphinan opioids | |
| Morphine (5 mM) | 21 ± 6 |
| Hydromorphone (5 mM) | 14 |
| Nalorphine (5 mM) | 51 |
| Naloxone (2.5 mM) | 14 |
| Naltrexone (2.5 mM) | 38 |
| Codeine (5 mM) | ND3-a |
| Oripavine opioids | |
| Buprenorphine (0.25 mM) | 55 ± 12 |
| Norburprenorphine (0.25 mM) | 130 ± 14 |
| Diprenorphine (0.25 mM) | 22 |
Assays were performed at pH 8.0 and 37°C for 0.5–1.0 hr, using whole-cell homogenates of HK293 cells expressing UGT1A3. The concentration of UDP-glucuronic acid was 2.0 mM, and the aglycone concentrations are indicated. Enzymatic rates are expressed as the mean ± SD of determinations from three transfections or the average determinations using cell homogenates from two transfections.
↵3-a ND, glucuronide formation was not detected (limits of detection, 2.0 pmol/min/mg of protein).