Michaelis-Menten Parameters for the Hydrolysis of Synthetic p-nitroanilide ( p-NA) Substrates by Human APC and Human Thrombin
| . | APC . | Thrombin . | ||||
|---|---|---|---|---|---|---|
| . | kcat (s−1) . | Km (mmol/L) . | s (mmol/L−1s−1) . | kcat (s−1) . | Km (mmol/L) . | s (mmol/L−1 s−1) . |
| S2266 | 8.4 ± 0.2 | 0.21 ± 0.01 | 40 ± 2 | 18.8 ± 0.5 | 0.18 ± 0.01 | 104 ± 8 |
| H-D-Asp-Arg-Arg-p-NA | 1.4 ± 0.1 | 0.49 ± 0.07 | 2.9 ± 0.5 | 0.13 ± 0.01 | 0.9 ± 0.1 | 0.21 ± 0.03 |
| H-L-Asp-Arg-Arg-p-NA | 18 ± 7 | 11 ± 5 | 1.6 ± 0.9 | 17.5 ± 0.3 | 0.146 ± 0.007 | 120 ± 6 |
| H-D-Trp-Arg-Arg-p-NA | 6.4 ± 0.2 | 0.084 ± 0.009 | 76 ± 8 | 0.38 ± 0.04 | 0.31 ± 0.08 | 1.2 ± 0.3 |
| H-L-Trp-Arg-Arg-p-NA | 0.24 ± 0.02 | 0.11 ± 0.03 | 2.2 ± 0.6 | 0.0088 ± 0.0004 | 0.060 ± 0.009 | 0.15 ± 0.02 |
| . | APC . | Thrombin . | ||||
|---|---|---|---|---|---|---|
| . | kcat (s−1) . | Km (mmol/L) . | s (mmol/L−1s−1) . | kcat (s−1) . | Km (mmol/L) . | s (mmol/L−1 s−1) . |
| S2266 | 8.4 ± 0.2 | 0.21 ± 0.01 | 40 ± 2 | 18.8 ± 0.5 | 0.18 ± 0.01 | 104 ± 8 |
| H-D-Asp-Arg-Arg-p-NA | 1.4 ± 0.1 | 0.49 ± 0.07 | 2.9 ± 0.5 | 0.13 ± 0.01 | 0.9 ± 0.1 | 0.21 ± 0.03 |
| H-L-Asp-Arg-Arg-p-NA | 18 ± 7 | 11 ± 5 | 1.6 ± 0.9 | 17.5 ± 0.3 | 0.146 ± 0.007 | 120 ± 6 |
| H-D-Trp-Arg-Arg-p-NA | 6.4 ± 0.2 | 0.084 ± 0.009 | 76 ± 8 | 0.38 ± 0.04 | 0.31 ± 0.08 | 1.2 ± 0.3 |
| H-L-Trp-Arg-Arg-p-NA | 0.24 ± 0.02 | 0.11 ± 0.03 | 2.2 ± 0.6 | 0.0088 ± 0.0004 | 0.060 ± 0.009 | 0.15 ± 0.02 |
Data were derived from initial velocity measurements under experimental conditions of 5 mmol/L Tris, 0.1% PEG, 200 mmol/L NaCl, pH 8.0, 25°C. The values of s determined in this manner agree with those measured independently and more accurately with the progress curve method (see Table 1).