SHEEP UTERUS DUAL LIPOXYGENASE IN THE SYNTHESIS OF 14,15-LEUKOTRIENES

Lipoxygenase was purified to homogeneity from sheep uterus cytosol usi ng a combination of ion exchangers, ammonium sulfate fractionation, an d gel filtration. The purified enzyme was found to be a homodimeric pr otein with monomer molecular weight of 66 kDa. When incubated with ara chidonic acid, the enzyme showed two lipoxygenase activities producing both 12- and 15-HPETEs at the optimum pH of 5.5. The relative concent ration of 12- and 15-HETEs, however, changed with the pH of the reacti on, 12-HETE being higher in the alkaline range and 15-HETE being highe r in the acidic range. Furthermore the enzyme showed the expected dual lipoxygenase based 14,15-LTA(4) synthase activity as evidenced by the formation of 8,15-diHETEs, the hydrolysis products of 14,15-LTA(4). I solation of 14,15-LTC(4) from the homogenates of sheep uterus gave fur ther evidence on the formation of leukotrienes. This is the first repo rt of the formation of 14,15-series leukotrienes in mammalian reproduc tive tissue. (C) 1994 Academic Press, Inc.