TABLE 2.
Thiosulfate oxidation of AvTsdA and MpTsdBA with ferricyanide and HiPIP
Enzyme assays with AvTsdA were performed in 100 mm ammonium acetate buffer, pH 4, at 30 °C with 8 nm enzyme. Activity measurements with MpTsdBA were performed in 100 mm ammonium acetate buffer, pH 5.2, with 200 mm NaCl at 25 °C and with 3.9 nm enzyme. In assays with HiPIP as electron acceptor, 10 μm HiPIP and 40 μm ferricyanide were used, and absorbance at 480 nm was followed. In activity assays with ferricyanide as electron acceptor, 1 mm ferricyanide was used, and the absorbance at 420 nm was measured. The units for Vmax are μmol min−1 mg protein−1. v versus [S] plots were fitted to the Hill equation.
| Electron acceptor | Enzyme | Vmax | S0.5 | kcat | cat/S0.5 |
|---|---|---|---|---|---|
| units mg−1 | μm | s−1 | mm−1 s−1 | ||
| Ferricyanide | AvTsdA | 31,419 ± 2408 | 835 ± 119 | 14,091 | 16,875 |
| MpTsdBA | 3011 ± 108 | 179 ± 21 | 2794 | 15,611 | |
| HiPIP | AvTsdA | 96 ± 3 | 27 ± 2 | 43 | 1595 |
| MpTsdBA | 26 ± 1 | 6 ± 0 | 24 | 4000 |