Novel membrane-associated prostaglandin E synthase-2 from crustacean arthropods.

Prostaglandins (PG) have been shown to play important physiological roles in insects and marine invertebrates, yet the knowledge of their biosynthetic pathways is often lacking. Recently, we described cyclooxygenases in two amphipod crustaceans, Gammarus sp. and Caprella sp.

Structural and catalytic insights into the algal prostaglandin H synthase reveal atypical features of the first non-animal cyclooxygenase.

Prostaglandin H synthases (PGHSs) have been identified in the majority of vertebrate and invertebrate animals, and most recently in the red alga Gracilaria vermiculophylla. Here we report on the cloning, expression and characterization of the algal PGHS, which shares only about 20% of the amino acid sequence identity with its animal counterparts, yet catalyzes the conversion of arachidonic acid into prostaglandin-endoperoxides, PGG2 and PGH2. The algal PGHS lacks structural elements identified in all known animal PGHSs, such as epidermal growth factor-like domain and helix B in the membrane binding domain.

Direct evidence of the cyclooxygenase pathway of prostaglandin synthesis in arthropods: genetic and biochemical characterization of two crustacean cyclooxygenases.

Prostaglandins, well-known lipid mediators in vertebrate animals, have also shown to play certain regulatory roles in insects and other arthropods acting on reproduction, immune system and ion transport. However, knowledge of their biosynthetic pathways in arthropods is lacking. In the present study, we report the cloning and expression of cyclooxygenase (COX) from amphipod crustaceans Gammarus spp and Caprella spp.

Identification of a functional allene oxide synthase-lipoxygenase fusion protein in the soft coral Gersemia fruticosa suggests the generality of this pathway in octocorals.

The conversion of fatty acid hydroperoxides to allene epoxides is catalysed by a cytochrome P450 in plants. In contrast, in the coral Plexaura homomalla, a catalase-related hemoprotein fused to the lipoxygenase (LOX) was found to function as an allene oxide synthase. This work reports the homology-based RT-PCR cloning and functional expression of a Gersemia fruticosa analogue of the allene oxide synthase-lipoxygenase (AOS-LOX) fusion protein.

A critical role of non-active site residues on cyclooxygenase helices 5 and 6 in the control of prostaglandin stereochemistry at carbon 15.

The correct stereochemistry of prostaglandins is a prerequisite of their biological activity and thus is under a strict enzymatic control. Recently, we cloned and characterized two cyclooxygenase (COX) isoforms in the coral Plexaura homomalla that share 97% amino acid sequence identity, yet form prostaglandins with opposite stereochemistry at carbon 15. The difference in oxygenation specificity is only partially accounted for by the single amino acid substitution in the active site (Ile or Val at position 349).

Structural and functional comparison of 15S- and 15R-specific cyclooxygenases from the coral Plexaura homomalla.

It has been known for 30 years that the gorgonian coral Plexaura homomalla contains either 15S- or 15R-configuration prostaglandins (PGs), depending on its location in the Caribbean. Recently we showed that the 15R-PGs in the R-variety of P. homomalla are formed by a unique cyclooxygenase (COX) with 15R oxygenation specificity [Valmsen, K.

The origin of 15R-prostaglandins in the Caribbean coral Plexaura homomalla: molecular cloning and expression of a novel cyclooxygenase.

The highest concentrations of prostaglandins in nature are found in the Caribbean gorgonian Plexaura homomalla. Depending on its geographical location, this coral contains prostaglandins with typical mammalian stereochemistry (15S-hydroxy) or the unusual 15R-prostaglandins. Their metabolic origin has remained the subject of mechanistic speculations for three decades.

The basis of prostaglandin synthesis in coral: molecular cloning and expression of a cyclooxygenase from the Arctic soft coral Gersemia fruticosa.

In vertebrates, the synthesis of prostaglandin hormones is catalyzed by cyclooxygenase (COX)-1, a constitutively expressed enzyme with physiological functions, and COX-2, induced in inflammation and cancer. Prostaglandins have been detected in high concentrations in certain corals, and previous evidence suggested their biosynthesis through a lipoxygenase-allene oxide pathway. Here we describe the discovery of an ancestor of cyclooxygenases that is responsible for prostaglandin biosynthesis in coral.

Evidence of a cyclooxygenase-related prostaglandin synthesis in coral. The allene oxide pathway is not involved in prostaglandin biosynthesis.

Certain corals are rich natural sources of prostaglandins, the metabolic origin of which has remained undefined. By analogy with the lipoxygenase/allene oxide synthase pathway to jasmonic acid in plants, the presence of (8R)-lipoxygenase and allene oxide synthase in the coral Plexaura homomalla suggested a potential metabolic route to prostaglandins (Brash, A. R.