Table 1.
Specific activity and kinetic constants of mammalian MsrBs
| Protein | Specific activity (nmol/min/mg protein) | Km (mM) | kcat (s-1) | kcat/Km (M-1 s-1) |
|---|---|---|---|---|
| MsrB1-Sec/SECIS | 1560 | 1.0 | 2.28 | 2280 |
| MsrB1-Cys/SECIS | 1.6 | 0.9 | 0.02 | 22 |
| MsrB1-Cys | 2.1 | 1.1 | 0.03 | 27 |
| MsrB2 | 353 | 0.17 | 0.23 | 1353 |
| MsrB3 | 423 | 2.9 | 2.29 | 790 |
Enzyme activity was determined using dabsyl-Met-R-SO as described in MATERIALS AND METHODS. The purified MsrB3Δ(1-31) lacking the N-terminal signal peptide was used as MsrB3. The specific activity was determined at 200 μM dabsyl-Met-R-SO. For determination of Km the range of concentration from 50 to 800 μM of dabsyl-Met-R-SO was used except for MsrB2, where the substrate concentration varied from 25 to 200 μM. All values are the average of three measurements and the standard deviations for all values are ≤20%.