Table 1

Characteristics of six human livers

Used for	Human Liver	R/S Ratio	S-Mephenytoin 4′-Hydroxylation		Desipramine 2-Hydroxylation
Used for	Human Liver	R/S Ratio	K_m (μM)	V_max (pmol/mg/min)	V_max/K_m (μl/mg/min)	Putative Phenotype	K_m (μM)	V_max (pmol/mg/min)	V_max/K_m (μl/mg/min)
Kinetic^1-a and inhibition studies	HL -32	0.75	25.9	20	0.78	PM	3.28	282	85.8
Kinetic^1-a and inhibition studies	HL -33	0.10	18.2	98	5.36	EM	6.94	89	12.8
Kinetic^1-a and inhibition studies	HL -34	0.06	5.5	305	19.69	EM	3.27	240	73.4
Kinetic^1-a study	HL -35	0.83	74.8	12	0.16	PM	9.97	53	5.3
Kinetic^1-a and inhibition studies	HL -36	0.06	22.0	217	9.87	EM	4.69	484	103.1
Kinetic^1-a and inhibition studies	HL -37	0.40	29.1	15	0.42	PM	8.48	102	12.0

R/S was determined as the ratio of the formation rate of 4′-hydroxymephenytoin with 1 mM of R-mephenytoin to that with 1 mM of S-mephenytoin. Microsomal samples with a ratio >0.7 were classified as those derived from the putative PM patients. However, HL-37 was identified as a putative PM liver by its lowerV _max andV _max/K _m values, although the R/S value obtained from this liver was <0.7.

↵1-a Kinetic study for Eadie-Hoffstee plots.