TABLE 3.
Steady-state kinetic measurements for wild-type and mutant Xyl3A with pNPX
| Protein | kcat (s−1) | Km (mM) | kcat/Km (mM−1s−1) | rkcat (%)c |
|---|---|---|---|---|
| Wild typea | 9.7 ± 0.3 | 1.8 ± 0.2 | 5.4 ± 0.6 | 100 |
| R149Lb | (2.5 ± 0.2) × 10−2 | ND | ND | 0.26 |
| Y237Fa | 1.6 ± 0.08 | 3.9 ± 0.5 | 0.41 ± 0.06 | 16 |
| D269Ab | (1.2 ± 0.5) × 10−2 | ND | ND | 0.12 |
| D269Nb | (2.2 ± 1.0) × 10−1 | ND | ND | 2.3 |
| E594Qa | 10 ± 0.2 | 2.0 ± 0.1 | 5.0 ± 0.3 | 103 |
| E616Aa | 3.3 ± 0.1 | 18 ± 1 | 0.2 ± 0.01 | 34 |
a
Error estimates are from propagating errors from nonlinear regression analysis utilizing GraphPad Prism v5.01.
b
The reported kcat value is kcat(apparent), as Km values were not determined; rates for these two mutants were determined at 10 mM pNPX concentration and thus represent a lower boundary on kcat. Each kcat determination was performed in triplicate, and data are means ± standard deviations from the mean.
c
rkcat, residual kcat.