TABLE 1

Kinetic parameters of benzydamine N-oxygenation and sulindac sulfide S-oxygenation by recombinant FMO proteins and liver microsomes from marmosets

Kinetic parameters were calculated from fitted curves by nonlinear regression and are presented as means ± S.E.

Enzyme SourceBenzydamine N-OxygenationSulindac Sulfide S-Oxygenation
KmVmaxaVmax/KmbKmVmaxVmax/Km
μMnmol/min per mg proteinml/min per mg proteinμMnmol/min per mg proteinml/min per mg protein
Liver microsomes47 ± 93.8 ± 0.20.08123 ± 142.7 ± 0.40.12
Marmoset FMO140 ± 100.76 ± 0.040.01943 ± 1523 ± 20.53
Marmoset FMO321 ± 427 ± 11.338 ± 1331 ± 20.80
  • Each substrate (10–1000 µM) was incubated with liver microsomes (0.05 mg protein) and recombinant proteins (10 pmol equivalent) at 37°C for 10–15 minutes in the presence of an NADPH-generating system.

  • a Vmax values for marmosets are given in nanomoles per minute per nanomole FMO.

  • b Vmax/Km values for marmosets are given in milliliters per minute per nanomole FMO.