Table 1.
Kinetic properties of the single, double, and triple mutants of the residues that bind the α-carboxyl of arginine in human arginase type I.
| Arginine | Agmatine | ||||||
|---|---|---|---|---|---|---|---|
| Enzyme | kcat | Km | kcat/Km | Kiorn | kcat | Km | kcat/Km |
| (s−1) | (mM) | (M−1s−1) | (mM) | (s−1) | (mM) | (M−1s−1) | |
| N130D | 33 | 13.3 | 2.5 × 103 | 7.8 | 3.0 | 1.4 | 2.1 × 103 |
| S137C | 75 | 3.2 | 2.3 × 104 | 7.6 | 1.8 | 7.5 | 2.4 × 102 |
| N139D | 64 | 4.4 | 1.4 × 104 | 6.2 | 1.3 | 5.3 | 2.5 × 102 |
| N130D-S137C | 23 | 6.5 | 3.5 × 103 | 7.1 | 2.3 | 1.7 | 1.3 × 103 |
| N130D-N139D | 33 | 6.1 | 5.4 × 103 | 6.4 | 1.6 | 1.1 | 1.4 × 103 |
| S137C-N139D | 83 | 10.8 | 7.7 × 103 | 8.4 | 1.1 | 0.9 | 1.2 × 103 |
| N130D-S137C-N139D | 4 | 6.9 | 5.8 × 102 | 5.4 | 0.9 | 1.6 | 5.6 × 102 |
| WT-arginase | 190 | 1.5 | 1.3 × 105 | 1.0 | n/a | ||
| E. coli-agmatinase | n/a | 120 | 1.1 | 1.1 × 105 | |||
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.