TABLE 4

Kinetic parameters of 5′-DFCR formation from capecitabine in the combination of human liver microsomes and cytosol, microsomes, and cytosol Capecitabine (0.05—3 mM) was incubated with the combination of microsomes and cytosol (1.2 mg/ml), microsomes (0.2 mg/ml), and cytosol (1.0 mg/ml) obtained from BD Gentest for 30 min in the presence of THU (500 μM), TPI (0.1 μM), and CDHP (100 μM). The kinetic parameters were calculated from the fitted curves by nonlinear regression.


Enzyme Source

Km

Vmax

Vmax/Km
mM pmol/min/mg protein nl/min/mg
Microsomes + cytosol 3.8 136.1 35.6
Microsomes 3.4 420.2 122.9
Cytosol
1.5
40.1
26.4