Kinetic parameters of enzyme-catalyzed oxygenation of TAZ and methimazole
TAZ assays were performed in triplicate on batches of microsomes isolated from three independent infections of Sf9 cells (i.e., nine measurements per FMO). Methimazole assays were performed in triplicate on a single batch of microsomes for each heterologously expressed human FMO. EtaA assays were performed in triplicate on purified protein. Kinetic parameters are reported as mean ± S.E.
Enzyme | Thiacetazone | Methimazole | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| KM | kcat | kcat/KM | KM | kcat | kcat/KM | |||||
| μM | min-1 | min-1 M-1 (×105) | μM | min-1 | min-1 M-1 (×104) | |||||
| FMO1 | 6.30 ± 0.80 | 5.08 ± 0.46 | 7.94 ± 1.99 | 8.08 ± 2.35 | 2.27 ± 0.30 | 28.11 ± 7.95 | ||||
| FMO2.1 | 5.80 ± 0.55 | 80.10 ± 4.42 | 142.56 ± 18.30 | 575.75 ± 60.02 | 31.50 ± 2.11 | 5.48 ± 0.68 | ||||
| FMO3 | 7.01 ± 0.53 | 1.37 ± 0.20 | 1.96 ± 0.39 | 29.30 ± 4.06 | 2.60 ± 0.38 | 8.97 ± 1.81 | ||||
| EtaA | 9.05 ± 0.57 | 3.02 ± 0.30 | 3.29 ± 0.81 | N.D. | N.D. | N.D. | ||||
N.D., not determined.