[Inactivation of prostaglandin H synthase from sheep vesicular glands with acetylenic fatty acids].

Acetylenic fatty acids, 8,11,14-eicosatrienoic, 5,8,11,14-eicosatetraenoic and 5,8,11,14,17-eicosapentaenoic acids, were compared with respect to their effects on the particulate prostaglandin H synthase. All the acetylenic acids inactivated the enzyme in a time-dependent manner. The eicosatriynoic and eicosatetraynoic acids exhibited comparable efficacies, whereas the eicosapentaenoic acid proved to be a weaker inactivator. The time-courses of inactivation fitted a kinetic model suggest an enzyme-catalysed conversion of the compounds via alternative suicidal and non-suicidal routes. The characteristics of inactivation of prostaglandin H synthase differ from those of lipoxygenases.