Table 1.
Observed rate constants for different oxygen-induced radical intermediates of iNOSox obtained during single turnover reaction by Stopped–flow and RFQ EPR.
| iNOSox1 | +BH4, +L-arg | +BH4, −L-arg | −BH4, +L-arg | −BH4, −L-arg |
|---|---|---|---|---|
| Fe(II)-O2 formation (s−1) | 106 ± 7 | 108 ± 1 | ND3 | ND |
| Fe(II)-O2 decay (s−1) | 18.0 ± 3.7 | 54 ± 8 and 2.62 | 3.3 ± 2.5 | 7.3 ± 1.2 |
| Reduction of cyt c | 8 ± 4 % | 36 ± 12 % | 91± 10 % | 80 ± 17 % |
| Type of radical | BH4+· | BH4+· and O2−· | O2−· | O2−· |
| Radical formation (s−1) | 20.0 ± 2.5 | 66 ± 16 | ND | ND |
| Radical decay (s−1) | 0.8 ± 0.2 | 1.2 ± 0.3 | 2.5 ± 0.5 | 4.5±1 |
| Heme oxidation (s−1) | 15 ± 4 | 70 ± 19 | ND | ND |
1
Anaerobic ferrous iNOSox was rapidly mixed with air-saturated buffer at 22 °C. Observed changes were followed either by Stopped-flow or RFQ EPR. For more details see Material and Methods.
2
Biphasic decay, 2nd slow face ~15%.
3
ND - Not Detectable
*
Standard error, n = 3