Substrate | FMO1 | FMO3 | ||||
---|---|---|---|---|---|---|
Km | Vmax | Vmax/Km | Km | Vmax | Vmax/Km | |
SAC | 4.1 | 6.1 | 1.5 | 5.5 | 18.2 | 3.3 |
DCVC | N.D. | N.D. | N.D. | 53.6 | 3.0 | 0.06 |
TCVC | N.D. | N.D. | N.D. | 7.7 | 0.06 | 0.01 |
Kinetic constants were determined as described in Experimental Procedures using double-reciprocal plots, all r values > 0.98. Units for Km are mm, units for Vmax are nmol sulfoxide/nmol flavin·min. Incubations contained 2 mm NADPH, 1 mm AOAA, and the following concentrations of substrate: 5–30 mm SAC with FMO1, 1–20 mm SAC with FMO3, 10–50 mmDCVC, and 2.5–15 mm TCVC. N.D., TCVC and DCVC kinetics were not determined with FMO1 due to no detectable activity at 10 mM substrate. SAC-apparent kinetic constants with FMO2 were:Km = 45.0, Vmax = 9.5, and Vmax/Km = 0.21.