In the last decade our laboratory has been investigating arachidonate 12-lipoxy-genase intensively and extensively.1.2 The enzyme oxygenates the position 12 of arachidonic acid, and produces 12S-hydroperoxy-5,8,10,14-eicosatetraenoic acid. When we investigated the substrate specificity of 4 purified preparations of 12-lipoxygenase,3,4 the enzymes of human and bovine platelets showed a relatively narrow specificity in terms of carbon chain length. These enzymes were most active with arachidonic acid and other C20 unsaturated fatty acids, but almost inactive with C18 acids such as linoleic and linolenic acids. In sharp contrast, 12-lipoxygenases of porcine and bovine leukocytes were active with linoleic and linolenic acids as well as arachidonic acid. As summarized in Table 1, the 12-lipoxygenases of leukocytes and platelets were also distinguished by the cross-reactivity of their antibodies and by the homology of their amino acid sequences.2 The leukocyte-type enzymes were found not only in leukocytes of various animal species but also in bovine trachea, porcine pituitary, canine brain, and rat and mouse pineal glands. The platelet-type 12-lipoxygenases were found in human and murine skin in addition to platelets of various animal species.2 In this chapter we would discuss two topics from our recent studies on the enzymes; 1) the suicide inactivation of 12-lipoxygenase, and 2) the transcriptional regulation of 12-lipoxygenase gene.
KeywordsEicosatetraenoic Acid Human Erythroleukemia Cell Bovine Platelet Suicide Inactivation Bovine Leukocyte
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