Molecular cloning, functional expression, and selective regulation of ovine prostaglandin H synthase-2

Structural characterization for ovine prostaglandin H synthase-1 (PGHS-1) is extensive, but the corresponding structure for the homologous ovine PGHS-2 isoform is undefined. Accordingly, we isolated a full-length (3.4 kb) ovine PGHS-2 cDNA from a primary-culture cell model (ovine tracheal epithelial cells) originally described as containing both PGHS isoforms. Analysis of ovine PGHS-2 cDNA sequence indicated conservation of critical amino acid residues, but differences in other hydrophilic regions allowed for the development of an anti-peptide antibody highly selective for PGHS-2. Enzymatic activities of the recombinant ovine PGHS isozymes indicated significant differences in response to aspirin-acetylation consistent with the characteristics of endogenous cellular PGHS activities under basal and serum-induced conditions. The results fully account for previous evidence of two distinct PGHS activities in cultured airway epithelial cells and provide for additional definition of PGHS structure-function relationships.