Table 1. NO uptake by purified PGHS-2.
NO (3.8 μM) was added to 80 mM Tris buffer, pH 7.8, at 37 °C containing H2O2 (500 μM) or 15(S)-HPETE (6.2 μM). Once the electrode response had stabilized, PGHS-2 (20 nM), apo-PGHS-2 (20 nM) or haematin (40 nM) was added, and rates of NO consumption were recorded. *For these samples, rates of NO loss at 3.0 μM were determined using the calculated first-order rate constant (kobs). For all other samples, initial linear rates of NO loss on addition of PGHS-2 were determined. Values are means±S.D.; n=3. For all kobs values, r2=0.99. ND, not determined.
| Sample | Rate (nmol·min−1) | kobs (s−1) |
|---|---|---|
| Background* | 0.7±0.09 | (7.86±1.0)×10−3 |
| +HPETE* | 0.6±0.03 | (6.93±0.36)×10−3 |
| +H2O2* | 0.77±0.1 | (8.6±1.2)×10−3 |
| +PGHS-2* | 0.75±0.02 | (8.5±0.2)×10−3 |
| +Apo-PGHS-2+HPETE* | 0.58±0.05 | (6.54±0.6)×10−3 |
| +Haematin+HPETE | 0.8±0.15 | ND |
| +PGHS-2+HPETE | 2.38±0.28 | ND |
| +Apo-PGHS-2+H2O2* | 0.81±0.07 | (9.06±0.8)×10−3 |
| +Haematin+H2O2* | 0.8±0.01 | (8.96±1.3)×10−3 |
| +PGHS-2+H2O2 | 2.1±0.3 | ND |