Table III.
Kinetic parameters of wild-type and selected SC PEP variants
| Variant no. | kcat/Km [=] (mM) s−1, pH 6.0 | R2 | kcat/Km [=] (mM) s−1, pH 4.5 | R2 | ki (min−1), 0.6 mg/ml pepsin | ki (min−1), 0.3 mg/ml pepsin |
|---|---|---|---|---|---|---|
| OPT | 24.5 | 0.99 | 6.4 | 0.97 | >10 | >10 |
| 10186 | 22.2 | 0.99 | 5.9 | 0.99 | 0.55 | 0.43 |
| 10187 | 22.7 | 0.97 | 7.9 | 0.95 | 0.92 | 0.61 |
| 10189 | 24.0 | 0.92 | 5.5 | 0.99 | 0.05 | 0.04 |
| 10194 | 20.9 | 0.92 | 5.2 | 0.95 | 0.39 | 0.21 |
| 10196 | 19.8 | 0.98 | 4.7 | 0.93 | 0.08 | 0.04 |
| 10205 | 23.2 | 0.97 | 4.3 | 0.87 | 0.05 | 0.02 |
| 10219 | 17.6 | 0.96 | 5.5 | 0.93 | 0.08 | 0.08 |
| 10224 | 27.6 | 0.99 | 7.0 | 0.93 | 0.24 | 0.12 |
| 10230 | 19.1 | 1.00 | 6.2 | 0.98 | 0.63 | 0.39 |
kcat/Km values were determined for each enzyme at pH 4.5 and pH 6.0. The first-order inactivation constant was measured at two different pepsin concentrations by comparing protein activity at pH 4.5 in the presence of a given pepsin concentration to the protein activity in the absence of pepsin. R2 values are listed for the fit of the V versus [S] curve used to calculate the kcat/Km values.