Table 5. Activity analysis of cABC I mutants.
Kinetic parameters are reported in μM (Km) and min−1 (kcat). n.d., activity was too low to be detected.+refers to an exhaustive digestion of the substrate; − indicates that no products were detected.
| C6S kinetics | DS kinetics | Activity on CE | |||||
|---|---|---|---|---|---|---|---|
| cABC I mutant | Km | kcat | Km | kcat | C6S | C4S | DS |
| His501→Ala | n.d. | n.d. | n.d. | n.d. | − | − | − |
| His561→Ala | 15.2 | 39100 | 6.90 | 3970 | + | + | + |
| His712→Ala | 8.60 | 1140 | 5.10 | 613 | + | + | + |
| Tyr508→Ala | n.d. | n.d. | n.d. | n.d. | − | − | − |
| Arg560→Ala | n.d. | n.d. | n.d. | n.d. | − | − | −* |
| Arg500→Ala | 19.9 | 419 | 35.7 | 162 | + | + | + |
| Glu653→Ala | n.d. | n.d. | n.d. | n.d. | − | − | − |
* The Arg560→Ala mutant did display some residual activity on DS.