TABLE 1

Kinetic constants for morphine 3- and 6-glucuronide formation by human recombinant UDP-glucuronosyltransferases calculated from Michaelis-Menten models

Isoform/Pathway	Apparent K_m^a	V_max ^a
	mM	pmol/min·mg
UGT1A1/3MG	18.7±1.4	4.5±0.2
UGT1A3/3MG	3.2±0.3	10.3±0.6
UGT1A6/3MG	18.0±3.7	20.8±2.6
UGT1A8/3MG	2.6±0.3	12.9±1.0
UGT1A9/3MG	37.4±5.6	31.7±3.1
UGT1A10/3MG	12.6±2.6	628.2±92.4
UGT2B7/3MG^b	0.42±0.6	23.5±23.4
	58.3±3.2	183.3±15.4
UGT2B7/6MG^b	0.97±0.3	7.4±1.6
	13.7±4.0	21.6±2.2

↵ a Mean ± S.E
↵ b Values for high- and low-affinity components of morphine 3- and 6-glucuronidation by UGT2B7 from fitting to biphasic Michaelis-Menten model