Table 2. Sugar composition of the isomerization products from sucrose and the general catalytic characteristics of different NX-5 mutants.
| Enzyme | Specific activity (U/mg) | Glucose and fructose (%) | Isomaltulose (%) | Trehalulose (%) | Product ratio |
|---|---|---|---|---|---|
| Wild-type | 401.0±0.3 | 4.2±0.2 | 83.2±0.3 | 12.6±0.3 | 6.6:1.0 |
| F297A | 77.2±0.5 | 100 | 0 | 0 | — |
| F321A | 98.0±0.5 | 100 | 0 | 0 | — |
| R325D | 188.4±0.5 | 54.1±0.3 | 20.4±0.1 | 25.5±0.2 | 0.8:1.0 |
| R328D | 237.9±0.4 | 17.4±0.2 | 60.9±0.3 | 21.7±0.2 | 2.8:1.0 |
| ΔGlu332 | 186.0±0.2 | 8.3±0.2 | 79.4±0.2 | 12.3±0.1 | 6.5:1.0 |
| Mut1a | 205.0±0.3 | 7.4±0.2 | 41.7±0.2 | 50.9±0.2 | 0.8:1.0 |
| Mut2b | 387.7±0.5 | 6.0±0.1 | 46.6±0.2 | 47.4±0.3 | 1.0:1.0 |
The product ratio indicates the proportion of isomaltulose to trehalulose in the final reaction products.
a
Mut1: R335H/R336T/K337I/D338P
b
Mut2: A330L/ΔGlu332/R335H/R336T/K337I/D338P/W339R