TABLE 1

Enzyme kinetic parameters determined by nonlinear regression for formation of M1 and M2 from (+)-tramadol and (−)-tramadol by pooled DLMs (n = 27)

ActivityHigh-Affinity ActivityLow-Affinity Activity
KmVmaxVmax/KmKmVmaxVmax/KmΣVmax/Km
μMpmol/min per mg proteinml/min per g proteinμMpmol/min per mg proteinml/min per g protein
(+)-M17.0248355543290.636
(−)-M19.8929.3117130.119.4
(+)-M2694406.454428430.156.6
(−)-M2492354.624943180.124.7
  • The data points used for fitting were the average of two independent experiments performed in duplicate (data points shown in Fig. 4 with the curves of best fit). Fitted parameters included Km and Vmax, while intrinsic clearance (Vmax/Km) values were calculated. Data for (+)-M1 and (−)-M1 formation were best fit by a two-enzyme model. Kinetic parameters for high- and low-affinity activities, as well as the sum of the high and low intrinsic clearance values (ΣVmax/Km), are given.