Table II. Effect of metalloporphyrin supplementation on oxygenase activity measured in 0.1 m Tris, pH 7.8, with 0.025% Tween 20 and 150 µm 18:1n-9 at 30 °C.
| Metalloporphyrin added to preincubationa | Metalloporphyrin added to assayb | PADOX-1 relative oxygenase ratec | GST-PADOX-1 relative oxygenase rated |
|---|---|---|---|
| None | None | 1.00 | 1.00 |
| Heme (5.0 µm) | None | 1.02 ± 0.04 | 1.03 ± 0.01 |
| None | Heme (1 µm) | 1.20 ± 0.09 | 1.16 ± 0.04 |
| None | MnPPIX (1 µm) | 1.01 ± 0.05 | 1.00 ± 0.02 |
a
The concentration of holoenzyme added to the preincubation (calculated from A410 using an extinction coefficient of 140 mM−1 cm−1) was 3.5 µm for PADOX-1 and 1.8 µm for GST-PADOX-1.
b
Any metalloporphyrin in the preincubation was diluted 600-fold in the assay.
c
Control activity was 4.1 ± 0.1 nmol of O2/min.
d
Control activity was 9.6 ± 0.2 nmol of O2/min.