Cofactor Requirements of the Enzyme Synthesizing Prostaglandin in Bovine Seminal Vesicles

Abstract

The effects of various cofactors on prostaglandin formation from arachidonic acid by the microsomal enzyme of bovine seminal vesicles were studied. In addition to the known activators, reduced glutathione and hydroquinone, the enzyme system was found to be markedly stimulated by hemoglobin, myoglobin or hemin. From the specific effects of these cofactors on prostaglandin formation or oxygen uptake, or both, it seemed that heme compounds and hydroquinone were involved in the step in which molecular oxygen became attached to the unsaturated fatty acids, while reduced glutathione was involved in the subsequent step of reduction of the peroxide-type intermediate. The facts that hydroquinone could be replaced by ascorbate, and that the order of addition of reactants to the system markedly affected both the yield of prostaglandin and the rate of oxygen consumption suggested that a free radical was formed during prostaglandin biosynthesis.