TABLE 3.
α-Glucosidase and amylase activities of whole-cell extracts of strainsa
| Strain | Genotype | Growth substrate (carbon source) | Activityb (U/g of cell protein)
|
|
|---|---|---|---|---|
| α-Glucosidase | Amylase | |||
| BT5482 | One copy of malR in the chromosome | Glucose | 2.2 | <0.6 |
| Maltose | 60.3 | 49.1 | ||
| BT5482(pMALR) | One chromosomal malR and malR in trans | Glucose | 1.8 | <0.6 |
| Maltose | 148.5 | 88.1 | ||
| BTΩmalR(pMALR) | Disrupted chromosomal malR and malR in trans | Glucose | 1.8 | <0.6 |
| Maltose | 126.4 | 78.1 | ||
| Ms-1(pMALR) | Disrupted chromosomal susR and malR in trans | Glucose | ND | ND |
| Maltose | 6.3 | <0.6 | ||
| BTΩsusB1(pMALR) | Disrupted chromosomal susB and malR in trans | Glucose | ND | ND |
| Maltose | 3.7 | 80.0 | ||
a
For this assay, strains were grown on minimal medium containing glucose or maltose (0.3%).
b
The substrates used to detect α-glucosidase and amylase activities are p-nitrophenyl-α-d-glucopyranoside and 4-nitrophenyl-α-d-maltoheptaoside-4,6-O-ethylidene, respectively. One unit of activity was defined as one micromole of p-nitrophenol liberated per minute. This experiment was conducted in duplicate, and the variation between replicates was <10%. ND, not determined.