Prostaglandin synthetase activity of goat vesicular microsomes: Co-factor requirement and effect of calcium ions.

The effects of several co-factors and bivalent cations on the activity of prostaglandin synthetase isolated from goat seminal vesicles were studied. Ca2+ appears to play a regulatory role in the biosynthesis of prostaglandin E2 by goat vesicular microsomes as the normal parabolic time course of synthesis changed to a sigmoid curve in the presence of 4 mM Ca2+ and to nearly a hyperbolic pattern when the microsomes were preincubated with the metal ions. The Ca2+ modulated reaction showed increased rate of prostaglandin E2 synthesis only when the period of incubation was extended beyond 30 min. The co-factor requirement of the goat enzyme was similar to that of the bovine and ovine prostaglandin synthetase systems.