Table 2

Kinetics of glucuronidation with various opioid substrates using membrane preparations of HK293 cells stably expressing either UGT2B7Y or H using two different passages of cultured cells

SubstrateUGT2B7YUGT2B7H
Km (μM)Vmax pmol/min/mg proteinEfficiency μl/min/mg (×100)Km(μM)Vmax pmol/min/mg proteinEfficiency μl/min/mg (×100)
Morphine, 3-glu458, 4905050, 59001100, 1200633, 3314779, 3054754, 922
Morphine, 6-glu432, 670485, 749112, 111311, 236413, 498132, 211
Nalorphine77, 1212870, 36503700, 3000141, 1713990, 46702850, 2700
Naloxone50, 403750, 25507500, 630041, 603810, 45309300, 7550
Naltrexone140, 180840, 1130600, 60063, 2001000, 11201600, 560
Hydromorphone410, 5001450, 1770350, 350390, 3601500, 1600380, 450
Oxymorphone1360, 9005640, 6040400, 650540, 6707510, 85701385, 1285
Codeine230, 360190, 4083, 11791, 55097, 11012, 20
Buprenorphine3, 1580, 9001940022 ± 6 400 ± 40 1840
UDP-GlcUA100, 1501490, 11401490, 760250, 2105500, 48202200, 2300

The assays were performed as described in the Methodssection.