Table 4.
Kinetic characterization and inhibition studies of mutant species of loop B of type I human arginase.
| Arginine | Agmatine | Ornithine Inhibition | Kis (mM) | Guanidine Inhibition | Kis (mM) | |||
|---|---|---|---|---|---|---|---|---|
| Km (mM) | kcat (s−1) | kcat/Km (M−1 s−1) |
|
|
||||
| WT-arginase | 1.5 ± 0.5 | 190 ± 10 | 1.26 × 105 | n/a | Competitive | 2 ± 0.5 | Competitive | 60 ± 2 |
| D181T | 5.3 ± 0.8 | 191 ± 8 | 3.6 × 104 | n/a | Competitive | 1.6 ± 0.3 | Competitive | 85 ± 10 |
| V182E | 2.4 ± 0.2 | 187 ± 10 | 7.7 × 104 | n/a | Competitive | 3.2 ± 0.2 | Competitive | 89 ± 12 |
| D181T/V182E | 32 ± 5 | 188 ± 10 | 5.8 × 103 | n/a | Mixed |
Kis = 71 ± 12 Kii = 203 ± 28 |
Competitive | 80 ± 5 |
| D181T/V182E + ins F | 20 ± 5 | 8.1 ± 1 | 3.5 × 102 | n/a | Competitive | 18 ± 6 | Competitive | 70 ± 10 |
The values of the kinetic parameters indicated in this table correspond to the results of two experiments performed in duplicate and the standard deviations were not greater than 5%. n/a: indicates no activity with the respective substrate.