Table 1

Km and Vmax values for the oxidation of thiocarbamides catalyzed by human FMO1 expressed in insect cells

SubstrateKm Vmax
M nmol substrate oxidized/min/mg
Methimazole518.09  ± 0.46
Thiourea421.12  ± 0.75
Phenylthiourea320.16  ± 0.11

Activities were measured by following substrate-dependent thiocholine oxidation as described in the text. Also see Guo et al. (1992). Values are means ± S.E. of triplicate measurements for each preparation. Kinetic constants were obtained from reciprocal plots of velocity of substrate-dependent thiocholine oxidation versus substrate concentration above and below the concentration required to give half maximal velocity.

  • ND, activity not detected at the highest concentrations soluble in the reaction medium.