Cyclooxygenase catalysis is stimulated by its product, PGG2, and by other lipid hydroperoxides. The endoperoxide, PGH2, was not stimulatory. The results provide a direct demonstration of an essential role for lipid hydroperoxides in prostaglandin biosynthesis, and show how the biosynthetic intermediate PGG2 has a positive accelerative effect.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22460/1/0000001.pd