TABLE 1.
Computed and experimental rate constants for the binding of superoxide to different enzymes
| Enzyme | Ionic strength (mM) | pH | Experimental (107 M−1s−1) | Calculated (error)† (107 M−1s−1) |
|---|---|---|---|---|
| SOD-B | 20 | 7.0 | 380 | 380 (75) |
| ∞ | <170* | 140 (25) | ||
| SOD-P | 20 | 7.0 | 850 | 850 (150) |
| ∞ | – | 140 (30) | ||
| HRP | 100 | 5.0 | 1.7 | 1.2 (0.4) |
| ∞ | – | 0.8 (0.4) | ||
| MPO | 100 | 8.0 | 0.11 | 0.08 (0.05) |
| 100 | 5.0 | – | 1.1 (0.4) | |
| ∞ | – | 18 (2) | ||
| LPO | 100 | 7.0 | – | 5.8 (1.0) |
| 100 | 5.0 | – | 26 (3) | |
| ∞ | – | 12 (3) |
*
Value measured at 150 mM ionic strength.
†
Calculated values are rate constants for approach of a superoxide atom to within 8 Å of the metal ion, divided by 1.3 (See text for details).