Peroxidase-dependent deactivation of prostacyclin synthetase.

A study of the enzymes of the arachidonic acid cascade revealed a high sensitivity of prostacyclin synthetase and a complete resistance of thromboxane A2 synthetase to time-dependent destruction by an oxidant [Ox] released during the peroxidase-catalyzed reduction of hydroperoxy fatty acids. The destructive action of [Ox] derived from prostaglandin G1 (PGG1), 15-hydroperoxy-PGE1, 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid, and 12-hydroperoxy-5,8,10,14-eicosatetraenoic acid upon prostacyclin synthetase was prevented by 2-aminomethyl-4-t-butyl-6-iodophenol. On the other hand, deactivation resulting from PGG2 metabolism was neither time-dependent nor sensitive to 2-aminomethyl-4-t-butyl-6-iodophenol. The possibility that the action of [Ox] may alter the arachidonic acid cascade in favor of thromboxane A2 is discussed in view of its possible implications in inflammatory and other pathological processes.