Table 5.
Kinetic parameters of Thermobacillus xylanilyticus xylanase (Tx-Xyn) and mutants for hydrolyses involving either birchwood xylan (BWX) or LVWAX
| Mutant | Kinetic parametersa | SRc | |||||
|---|---|---|---|---|---|---|---|
| BWX | LVWAX | ||||||
| kcat(s-1) | KMb (g/l) | kcat/KMb (s-1/g/l) | kcat (s-1) | KMb (g/l) | kcat/Kmb (s-1/g/l) | ||
| Tx-Xyn | 610.5 ± 19.6 | 2.54 ± 0.19 | 242.1 | 1,699.4 ± 95.9 | 5.10 ± 0.09 | 333.1 | 0.73 |
| Y6H | 806.1 ± 61.2 | 2.37 ± 0.27 | 340.5 | 2,081.6 ± 16.4 | 5.73 ± 0.09 | 363.0 | 0.94 |
| S27T | 742.9 ± 22.4 | 1.93 ± 0.15 | 376.5 | 1,936.0 ± 19.2 | 4.81 ± 0.04 | 402.5 | 0.94 |
| Y111H | 449.3 ± 23.2 | 1.54 ± 0.14 | 292.0 | 1,889.0 ± 72.9 | 5.01 ± 0.07 | 376.7 | 0.78 |
| Y6H-Y111H | 433.1 ± 12.5 | 1.91 ± 0.11 | 226.8 | 1,834.7 ± 75.4 | 5.33 ± 0.35 | 345.9 | 0.66 |
| S27T-Y111H | 535.8 ± 30.2 | 1.72 ± 0.21 | 311.5 | 1,906.1 ± 4.4 | 4.39 ± 0.02 | 434.1 | 0.72 |
| Y3W | 704.5 ± 29.8 | 2.11 ± 0.14 | 333.4 | 1,743.0 ± 26.5 | 5.51 ± 0.02 | 316.3 | 1.05 |
| Y111S | 758.8 ± 15.9 | 2.12 ± 0.04 | 358.6 | 1,755.0 ± 106.3 | 4.75 ± 0.14 | 369.4 | 0.97 |
| Y111T | 905.2 ± 17.2 | 2.35 ± 0.15 | 369.4 | 1,740.4 ± 41.8 | 4.81 ± 0.06 | 361.4 | 1.02 |
aAll data presented are the result of triplicate experiments.
bThe heterogeneous nature of the substrate excludes the determination of a value for KM , thus values are apparent.
cRatio of the performance constants for a given enzyme.