Bacterial and algal orthologs of prostaglandin H2 synthase: novel insights into the evolution of an integral membrane protein

•Bioinformatics reveals a clade of bacterial/algal prostaglandin H2 synthase orthologs.•Phylogenetic analyses predict unique differences bacterial and eukaryotic orthologs.•An algal ortholog from G. vermiculophylla is a prostaglandin synthase.•A cyanobacterial ortholog from N. punctforme acts as a 10S-dioxygenase.•Substrates recognized by orthologs reflect the lipid composition of the organism.

Prostaglandin H2 synthase (PGHS; EC 1.14.99.1), a bi-functional heme enzyme that contains cyclooxygenase and peroxidase activities, plays a central role in the inflammatory response, pain, and blood clotting in higher eukaryotes. In this review, we discuss the progenitors of the mammalian enzyme by using modern bioinformatics and homology modeling to draw comparisons between this well-studied system and its orthologs from algae and bacterial sources. A clade of bacterial and algal orthologs is described that have salient structural features distinct from eukaryotic counterparts, including the lack of a dimerization and EGF-like domains, the absence of gene duplicates, and minimal membrane-binding domains. The functional implications of shared and variant features are discussed.

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