TABLE 2.
The Ki″ values are shown of ß-galactosidases with substitutions for the residues thought to be important for binding Glc for the intramolecular acceptor action of the enzyme
Ki″ is the dissociation constant of Glc from the acceptor site. k4 values for glucose are also shown. Values are also given for N460A-ß-galactosidase, a point mutant that affects transition state binding but is not expected to affect Glc binding. A dash indicates that the value was not meaningful.
| Ki″ | Fold poorer binding | k4 | |
|---|---|---|---|
| mm | s−1 | ||
| Native | 17 | — | 280 |
| Substituted enzymes | |||
| N102A | ∼670 | ∼40 | 185 |
| K517A | ∼175 | ∼10 | 135 |
| H418N | >335 | >20 | 50 |
| S796A | ∼390 | ∼23 | 20 |
| E797A | ∼139 | ∼8 | 285 |
| N460A | ∼23 | ∼1.3 | 20 |