Figure 3.

SNAP plus xanthine/xanthine oxidase activation of GSH-Px/GSH inhibited PGH synthase-1. PGH synthase-1 (75 nM) was incubated at 37°C in 1.3 ml 0.1 M NaPO₄ (pH 8.0) containing 500 μM phenol, 0.25 mM GSH, and 120 units GSH-Px. Following addition of 50 μM [1-¹⁴C]AA, 300 μM SNAP, and 100 μM xanthine plus 0.2 unit xanthine oxidase or both were added. Aliquots of the reaction mixture were removed at the indicated time points and terminated with ethyl ether/methanol/1 M citric acid (pH 4.0) (30:4:1). Radiolabeled prostaglandin products were quantitated as described in Fig. 1. Control PGH synthase-1 activity in the absence of GSH-Px was 395 pmol product/pmol PGH synthase-1. ▴, 300 μM SNAP; ○, 100 μM xanthine plus 0.2 unit xanthine oxidase; •, SNAP plus xanthine/xanthine oxidase.