Cloning of the cDNA for human 12-lipoxygenase.
 A full-length cDNA clone encoding 12-lipoxygenase (arachidonate:oxygen 12-oxidoreductase, EC 1.13.11.31) was isolated from a human platelet cDNA library by using a cDNA for human reticulocyte 15-lipoxygenase as probe for the initial screening.
 The cDNA had an open reading frame encoding 662 amino acid residues with a calculated molecular weight of 75,590.
 Three independent clones revealed minor heterogeneities in their DNA sequences.
 Thus, in three positions of the deduced amino acid sequence, there is a choice between two different amino acids.
 The deduced sequence from the clone plT3 showed 65% identity with human reticulocyte 15-lipoxygenase and 42% identity with human leukocyte 5-lipoxygenase.
 The 12-lipoxygenase cDNA recognized a 3.0-kilobase mRNA species in platelets and human erythroleukemia cells (HEL cells).
 Phorbol 12-tetradecanoyl 13-acetate induced megakaryocytic differentiation of HEL cells and 12-lipoxygenase activity and increased mRNA for 12-lipoxygenase.
 The identity of the cloned 12-lipoxygenase was assured by expression in a mammalian cell line (COS cells).
 Human platelet 12-lipoxygenase has been difficult to purify to homogeneity.
 The cloning of this cDNA will increase the possibilities to elucidate the structure and function of this enzyme.
