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 E2by 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 E2synthesis 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.
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