Substrate | Cytosol | Purified PST | Purification (fold) | ||
---|---|---|---|---|---|
Km (μM) | Vmax(nmol/min/mg) | Km (μM) | Vmax (nmol/min/mg) | ||
1-Naphthol (1.3–133) | 7 | 1.3 | 2 | 482 | 370 |
Vanillin (0.13–6.7) | 7 | 0.17 | 1 | 32.6 | 191 |
4-Nitrophenol (0.13–6.7) | 0.4 | 0.38 | 1 | 49.8 | 131 |
Tyramine (133–1333) | 500 | 0.15 | 225 | 15 | 100 |
5-HT (13.3–133) | 740 | 0.13 | 118 | 8.2 | 63 |
Dopamine (1.33–67) | 2 | 0.13 | 4 | 4.3 | 33 |
Enzyme activities were determined in duplicate, over the range of substrate concentrations in parentheses, on a single sample of dog liver cytosol or purified phenol sulfotransferase using either 1-[1-14C]naphthol or PAP35S (all other substrates) as described in Materials and Methods. Km and Vmax values were calculated using the Regression software package (Blackwell Scientific).