Prostaglandin endoperoxide E isomerase from bovine vesicular gland microsomes, a glutathione-requiring enzyme

Prostaglandin endoperoxide E isomerase catalyzes the isomerization of the endoperoxy group of prostaglandin H and produces prostaglandin E. The enzyme was solubilized with Tween 20 from bovine vesicular gland microsomes and purified 26-fold by successive column chromatography on DEAE-cellulose and omega-aminobutyl Sepharose 4B. The previously known requirement for glutathione was further investigated. The activity of freshly prepared enzyme was destroyed rapidly with a half-life of about 30 min at 24 degrees, pH 8.0. Various thiol compounds including glutathione protected the enzyme from such an inactivation. However, several findings indicated that glutathione was possibly specifically involved as a coenzyme in the isomerase reaction, but was not oxidized in a stoichiometric quantity. The enzyme also isomerized prostaglandin G at a rate approximately half of that of prostaglandin H.