THE HUMAN LEUKOTRIENE A(4) HYDROLASE GENE IS EXPRESSED IN 2 ALTERNATIVELY SPLICED MESSENGER-RNA FORMS

We identified a novel short (s-) mRNA of the human leukotriene-A(4) (L TA(4)) hydrolase using sequential reverse transcriptase PCR mapping. T he s-mRNA is generated by skipping an 83 bp exon located in the 3' cod ing region and suggests the expression of an LTA, hydrolase isoform wi th a calculated molecular mass of 59 kDa and a distinct C-terminus. Bo th LTA(4) hydrolase mRNAs are constitutively expressed in blood cells, endothelial cells, smooth muscle cells, fibroblasts and tumour cells. The ratios of their mRNA expression levels are cell specific, with re latively high s-form mRNA expression in reticulocytes. Our data strong ly suggest that the novel mRNA codes for the structurally related but distinct LTA(4) hydrolase isoenzyme that has been postulated.