Table 1. Steady state constants for chemical rescue of activity on R301A.
| k rescue (s−1) | K m, phosphite (mM) | k rescue/ K m, phosphite (M−1 s−1) | K R (mM) |
|
pK a a | D k cat | D k cat/K m | |
| 17X-PTDHb | 3.2 (0.2) | 0.028 (0.007) | 1.2 (0.3) x 105 | na | na | na | 2.3 (0.1) | 2.1 (0.2) |
| R301Kb | 4.5 (0.7) | 1.1 (0.1) | 4.0 (0.8) x 103 | na | na | na | 1.9 (0.1) | 2.2 (0.5) |
| R301Ab | 0.041 (0.007) | 20 (1) | 2.1 (0.4) | na | na | na | 2.7 (0.1) | 2.1 (0.2) |
| R301A+guanidine | 1.2 (0.1) | 30 (3) | 41 (4) | 18 (3) | 8.1 (0.1) | 13.6 | 1.8 (0.1) | 2.3 (0.1) |
| R301A+methylguanidine | 0.68 (0.04) | 130 (30) | 5.2 (1.1) | 55 (9) | 7.2 (0.1) | 13.4 | 1.4 (0.1) | 1.6 (0.5) |
| R301A+acetamidine | 0.86 (0.08) | 130 (20) | 6.7 (1.1) | 63 (15) | 6.3 (0.1) | 12.5 | 1.5 (0.1) | 1.8 (0.6) |
| R301A+aminoguanidine | 1.4 (0.1) | 7.4 (0.5) | 180 (10) | 32 (2) | 5.3 (0.1) | 11.0 | 2.1 (0.1) | 3.1 (0.3) |
| R301A+ethylguanidine | 0.52 (0.13) | nd | nd | 440 (190) | 6.1 (0.2) | 13.3 | nd | nd |
| R301A+N-guanylurea | 0.42 (0.07) | nd | nd | 120 (40) | −2.9 (0.2) | 3.9 | nd | nd |
The errors given in parentheses were obtained from fits of the experimental data to the appropriate equations. na = not applicable. nd = not determined. k rescue refers to k cat of the enzyme in cases where no rescue reagent was added (i.e. entries 1–3). aData from reference [48]. bData from reference [13].