Table 2.
Effect of SOD on the NADPH:Cit stoichiometry of NOS-I
| NOS-I | SOD, μM | Product formation,
nmol·mg−1·h−1
|
Ratio NADPH:Cit | Difference +SOD | |||
|---|---|---|---|---|---|---|---|
| n | Cit | n | NADP+ | ||||
| Porcine | 0 | 6 | 983.8 ± 45.1 | 6 | 1951 ± 145 | 1.98 | |
| 35.7 | 6 | 528.7 ± 9.9 | 6 | 603 ± 107 | 1.14 | −0.84 | |
| Human | 0 | 17 | 176.8 ± 7.4 | 4 | 290.7 ± 24.1 | 1.64 | |
| 35.7 | 3 | 67.9 ± 7.9 | 3 | 51.5 ± 13.7 | 0.76 | −0.88 | |
Native NOS-I purified from porcine cerebellum (0.4 μg) or recombinant NOS-I extracted as crude cytosolic fraction of Sf9 cells overexpressing the human NOS1 gene (30 μl) was incubated in the absence of GSH for 15 min as described in the text (NADP+ formation); for measurement of Arg-to-Cit conversion, nicotinamide was unnecessary and therefore omitted.