Molecular cloning and amino acid sequence of human 5-lipoxygenase.

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Abstract
5-Lipoxygenase (EC 1.13.11.34), a Ca2+- and ATP-requiring enzyme, catalyzes the first two steps in the biosynthesis of the peptidoleukotrienes and the chemotactic factor leukotriene B4. A cDNA clone corresponding to 5-lipoxygenase was isolated from a human lung .lambda.gt11 expression library by immunoscreening with a polyclonal antibody. Additional clones from a human placenta .lambda.gt11 cDNA library were obtained by plaque hybridization with the 32P-labeled lung cDNA clone. Sequence data obtained from several overlapping clones indicate that the composite cDNAs contain the complete coding region for the enzyme. From the deduced primary structure, 5-lipoxygenase encodes a 673 amino acid protein with a calculated molecular weight of 77,839. Direct analysis of the native protein and its proteolytic fragments confirmed the deduced composition, the amino-terminal amino acid sequence, and the structure of many internal segments. 5-Lipoxygenase has no apparent sequence homology with leukotriene A4 hydrolase or Ca2+-binding proteins. RNA blot analysis indicated substantial amounts of an mRNA species of .apprxeq. 2700 nucleotides in leukocytes, lung, and placenta.