Product Formation Approach | Substrate Depletion Approach | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
R/S | R | S | |||||||||
Km | Vmax | Vmax/Km | Km | Vmax | Vmax/Km | Km | Vmax | Vmax/Km | |||
DHMA | SULT1A1 | 3-Sulfate | 51 ± 6 | 3.3 ± 0.2 | 0.065 | ||||||
4-Sulfate | n.d. | n.d. | n.d. | ||||||||
SULT1A3 | 3-Sulfate | 0.8 ± 0.2 | 272 ± 17 | 340 | 0.4 ± 0.1 | 81 ± 17 | 203 | 0.7 ± 0.2 | 291 ± 45 | 416 | |
4-Sulfate | 0.5 ± 0.2 | 26 ± 2 | 52 | ||||||||
pHLC | 3-Sulfate | 1.3 ± 0.2 | 0.05 ± 0.002 | 0.038 | 1.3 ± 0.7 | 0.054 ± 0.003 | 0.042 | 1.0 ± 0.4 | 0.078 ± 0.007 | 0.078 | |
4-Sulfate | 1.6 ± 0.6 | 0.005 ± 0.001 | 0.003 | ||||||||
HMMA | SULT1A3 | 0.4 ± 0.1 | 410 ± 45 | 1025 | 0.4 ± 0.1 | 176 ± 18 | 440 | 0.4 ± 0.1 | 151 ± 15 | 378 | |
SULT1E1 | 75 ± 11 | 27 ± 2 | 0.36 | ||||||||
pHLC | 0.6 ± 0.1 | 0.16 ± 0.01 | 0.26 | 0.5 ± 0.1 | 0.040 ± 0.005 | 0.08 | 0.4 ± 0.1 | 0.035 ± 0.003 | 0.087 |
Km, μM; Vmax, nmol · min−1 · mg−1; n.d., not determined; ±, error of the calculated kinetic parameters.