Mechanisms of Cyclooxygenase and Peroxidase Catalysis by Prostaglandin H Synthase

Eicosanoids, the group of oxygenated arachidonic acid metabolites which includes prostaglandins, thromboxanes, leukotrienes, and various hydroperoxy and hydroxy fatty acids, have come to be implicated at several stages of carcinogenesis and metastasis. The exact roles played by the eicosanoids in the control of cell proliferation are difficult to discern at present, as the literature is filled with conflicting reports of their effects (for a review, see Ref. 1). The resolution of these apparently contradictory effects of eicosanoids will be aided by a close comparison of the concentrations of these eicosanoids which exist in vivo and those concentrations used in many in vitro experiments. An understanding of the details of the biosynthetic mechanisms for the eicosanoids, and the interplay among substrates and effectors in these reactions may also help in unravelling the tangle of conflicting reports.