TABLE 2.
IC50 (μm) of (GlcN)2–7 toward four chitinases and three mutants of OfChtI at 30 °C (pH 7.0)
| IC50 |
||||||
|---|---|---|---|---|---|---|
| (GlcN)2 | (GlcN)3 | (GlcN)4 | (GlcN)5 | (GlcN)6 | (GlcN)7 | |
| μm | ||||||
| OfChtIa | ||||||
| Wild type | 2375.5 ± 433.6 | 776.0 ± 95.2 | 204.2 ± 17.3 | 16.5 ± 2.2 | 14.5 ± 1.8 | 11.4 ± 2.1 |
| N305A | 2117.1 ± 521.7 | 802.5 ± 107.2 | 225.7 ± 23.7 | 17.1 ± 2.9 | 15.0 ± 2.5 | 11.9 ± 1.7 |
| Y37A | 2402.2 ± 415.5 | 787.4 ± 95.2 | 375.6 ± 28.6 | 157.3 ± 11.8 | 151.5 ± 19.7 | 104.0 ± 13.2 |
| W372Ab | ||||||
| F309A | 6671.9 ± 496.0 | 2284.5 ± 242.9 | 778.1 ± 39.3 | 68.4 ± 4.7 | 58.0 ± 2.8 | 53.3 ± 3.7 |
| HsChta | 3422.5 ± 744.1 | 1610.0 ± 176.7 | 637.4 ± 115.6 | 163.1 ± 19.9 | 69.5 ± 10.1 | 37.8 ± 8.6 |
| SmChiAa,c | 4125.3 ± 720.9 | 1700.2 ± 205.3 | 659.7 ± 98.9 | 356.4 ± 47.1 | 169.7 ± 21.3 | 168.0 ± 28.4 |
| (320.7 ± 35.8)d | (145.5 ± 18.3)d | |||||
| SmChiBa,c,e | 2997.5 ± 352.6 | 560.3 ± 114.4 | 298.8 ± 36.7 | 116.4 ± 15.4 | 72.8 ± 8.6 | 65.7 ± 10.1 |
| (89.3 ± 4.2)d | (52.4 ± 5.8)d | |||||
a The IC50 values of (GlcN)2–7 toward four chitinases were determined with a substrate concentration of 0.1 mm.
b W372A showed no activity against pNP-(GlcNAc)2.
c The Km values for the substrate pNP-(GlcNAc)2 for SmChiA and SmChiB were determined by using Lineweaver-Burk plots. The Km value is 734.1 ± 33.8 μm for SmChiA and 320.2 ± 28.5 μm for SmChiB. The substrate concentrations used were 0.02–0.5 mm.
d The Ki values for (GlcN)5 and (GlcN)6 for SmChiA and SmChiB were determined by using Dixon plots (supplemental Fig. S2). The substrate concentrations used were 0.075–0.3 mm.
e The IC50 value of (GlcN)5 toward SmChiB with MU-(GlcNAc)2 as substrate is 127.6 ± 11.9 μm.