Table 2

Km, Vmax, and Kcat/Km values for control and Es1e mouse plasma with CPT-11

SN-38 levels were determined by HPLC, and kinetic parameters were calculated from hyperbolic plots of V versus [S] for CPT-11 with each plasma sample.

PlasmaKmm)Vmax (pmol SN-38/min/ml)Goodness of fit (R)Kcat/Kma (s l)
Control2.35 ± 0.171761 ± 37.50.9789.55 ± 7.85
Es1 e 14.0 ± 1.4031 ± 0.90.950.136 ± 0.011
  • a Determined from the initial slope of the V versus [S] hyperbolic plots. Units are s−1 l−1 because reactions were performed with unknown enzyme concentrations but known plasma volumes.