TABLE 3.
Enzymatic activities of wild-type and mutant CbXyn10C on xylan and cellulosesa
| CbXyn10C enzyme | Sp act (μmol/min/μmol of enzyme) |
CMC |
Xylan |
(kcat/Km for CMC)/(kcat/Km for xylan) (10−4) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Avicel | Filter paper | MCC | kcat (s−1) | Km (mg ml−1) | kcat/Km (ml s−1 mg−1) | kcat (s−1) | Km (mg ml−1) | kcat/Km (ml s−1 mg−1) | ||
| Wild type | 3.4 ± 0.8 | 5.4 ± 0.3 | 2.3 ± 0.0 | 1.8 ± 0.0 | 4.3 ± 0.0 | 0.42 | 630 ± 16 | 0.3 ± 0.1 | 2,100 | 2.0 |
| Q94A | 2.4 ± 0.2 | 6.2 ± 0.4 | ND | 1.3 ± 0.1 | 4.0 ± 0.3 | 0.33 | 310 ± 12 | 0.3 ± 0.1 | 1,000 | 3.3 |
| L306A | 2.9 ± 0.1 | 6.5 ± 0.3 | ND | 1.0 ± 0.0 | 2.6 ± 0.0 | 0.38 | 390 ± 25 | 0.5 ± 0.1 | 780 | 4.9 |
| Q94A/L306A | 3.4 ± 0.1 | 6.2 ± 0.1 | ND | 0.8 ± 0.0 | 3.3 ± 0.0 | 0.24 | 360 ± 17 | 0.6 ± 0.1 | 600 | 4.0 |
| E140A | 0 | 0 | 0 | ND | ND | ND | ND | ND | ND | ND |
| E248A | 0 | 0 | 0 | ND | ND | ND | ND | ND | ND | ND |
| E140A/E248A | 0 | 0 | 0 | ND | ND | ND | ND | ND | ND | ND |
| CbXyn10C-CBM3b | 7.3 ± 0.0 | 12 ± 0.1 | 4.9 ± 0.0 | ND | ND | ND | ND | ND | ND | ND |
| CbXyn10C-CBM3b-CBM3b | 8.4 ± 0.0 | 14 ± 0.1 | 7.2 ± 0.0 | ND | ND | ND | ND | ND | ND | ND |
a
ND, not determined; MCC, microcrystalline cellulose with the amorphous region removed (Sigma).