Kinetics of glucuronide formation for selected opioids in membrane preparations from HK293 cells stably expressing UGT2B9 protein
| Substrate | ApparentKM | Vmax | Vmax/KM(×100) |
|---|---|---|---|
| μM | pmol/min × mg | ||
| Morphine | |||
| 3-Glucuronide | 330 ± 14 | 302 ± 11 | 92 |
| 6-Glucuronide | ND2-a | ND | |
| Codeine | 239, 156 | 82, 61 | 37 |
| Dihydromorphine | 980 ± 70 | 390 ± 28 | 40 |
| Hydromorphone | 1390 ± 280 | 570 ± 125 | 41 |
| Oxymorphone | 702, 775 | 237, 235 | 32 |
| Naloxone | 45, 48 | 35, 61 | 103 |
| Nalorphine | 60, 65 | 310, 280 | 475 |
| Naltrexone | 50, 67 | 19, 24 | 37 |
| Buprenorphine | 41, 40 | 46, 34 | 99 |
Apparent KM values for the aglycone substrates were determined using 2.0 mM UDP-glucuronic acid. All reactions were conducted at pH 8.0, except for that with buprenorphine, which was conducted at pH 7.0. Results are expressed as the mean ± SE for determinations made using membrane preparations from three different passages of cultured cells or as the individual values obtained using membrane preparations from two different passages of cultured cells. Kinetic values for morphine 6-glucuronide formation were not determined because of low rates of product formation.
↵2-a ND, not determined.