EVIDENCE FOR AN ACTIVATING FACTOR FORMED DURING PROSTAGLANDIN BIOSYNTHESIS

SUMMARY: The oxygenation of 5,8,11,14-eicosatetraenoic acid by acetone powder preparations of sheep vesicular glands proceeded with a lag or accelerative phase when inhibitory concentrations of NaCN were present. This accelerative feature of the reaction suggested that an activating material might be produced as the oxygenation reaction proceeds. When a second addition of fresh enzyme was made to a reaction mixture, the lag phase was as short as in uninhibited controls. This indicated that an activating factor was required for optimal activity of this dioxygenase, and that it accumulated during the oxygenation reaction in the presence of NaCN. The factor was extracted from an aqueous incubation medium with cold diethyl ether. There was a positive relationship between the amount of activating factor added and the resultant increase in the initial velocity of the oxygenation system. Oxygenation of 5,8,11,14-eicosatetraenoic acid by enzyme preparations from sheep vesicular glands was suppressed in the presence of functioning glutathione peroxidase activity (i) and, therefore, it was suggested that this phenol