The occurrence of two new prostaglandin derivatives (15-epi-PGA₂ and its acetate, methyl ester) in the Gorgonian $\text{Plexaura}$ $\text{Homomalla}$ Chemistry of Coelenterates. XV.

Use of nanoparticles has recently increased in a number of fields, including medicine, personal care products, the food industry, and the pharmaceutical industry. With continuous and growing use of nanoparticles in the environment, their residue can cause harmful effects in living beings. Studies have revealed more than 2300 products containing nanoparticles used by European consumers. Most types of nanoparticles are used in huge quantities. The influence of nanoparticles on marine organisms needs to be more carefully estimated using innovative developed technologies. Numerous marine organisms are involved in the food chain. Concerning the risk evaluation of nanoparticles on marine ecosystems, disturbing the food chain poses a large risk, as it could ultimately lead to changes in humans and other species. To examine such harmful effects, take the necessary action, and overcome toxicity, further investigations are urgently required.

In this essay we provide a comprehensive update on the biology and molecular biology of prostaglandins (PGs) and other eicosanoids in insects. Phospholipase A₂ (PLA₂) is the first biochemical step in eicosanoid biosynthesis. Cellular and secretory PLA₂ types, similar to those of vertebrates, have been identified and demonstrated to act in insect eicosanoid biosynthesis. However, eicosanoid biosynthetic pathways in insects are not identical to those of vertebrates. The relatively low concentrations of arachidonic acid (AA) in phospholipids of insect tissues suggest that PLA₂ may hydrolyse linoleic acid as a precursor of eicosanoid biosynthesis and its subsequent desaturation and elongation leads to AA. Unlike vertebrates, AA is not oxidized by cyclooxygenase, but by a specific peroxidase called peroxinectin to produce a prostaglandin (PG) precursor, PGH₂, which is then isomerized into PGE₂ by PGE₂ synthase. PGs and other eicosanoids mediate insect reproduction such as oocyte development and egg-laying behaviour, trehalose metabolism, fluid secretion, and immunity. They also interact with insect cytokine and other immune mediators to propagate non-self recognition signals to immune effector tissues. In the cross-talks, eicosanoids act as downstream signals because any intervention of eicosanoid signalling leads to substantial immunosuppression. Because host immunosuppression favours pathogens, some entomopathogens exploit a PLA₂ inhibitory strategy to express their virulence. We propose PGs and other eicosanoids as central signalling systems in insect biology.

Methods are presented for the use of the coral 8R-lipoxygenase from the Caribbean sea whip coral Plexaura homomalla as a model enzyme for structural studies of animal lipoxygenases. The 8R-lipoxygenase is remarkably stable and can be stored at 4°C for 3 months with virtually no loss of activity. In addition, an engineered “pseudo wild-type” enzyme is soluble in the absence of detergents, which helps facilitate the preparation of enzyme:substrate complexes.

Prostaglandins (PGs) belong to a subclass of eicosanoids and are classified based on the structures of the cyclopentane ring and their number of double bonds in their hydrocarbon structures. PGs are important lipid mediators that are involved in inflammatory response. The biosynthesis of diverse PGs from unsaturated C20 fatty acids containing at least three double bonds such as dihomo-γ-linoleic acid (20:3^Δ8Z,11Z,14Z), arachidonic acid (20:4^{Δ5Z,8Z,11Z,14Z}), and eicosapentaenoic acid (20:5^{Δ5Z,8Z,11Z,14Z,17Z}) is enables by various PG synthases, including prostaglandin H synthase (PGHS), 15-hydroxyprostaglandin dehydrogenase (15-HPGD), PGES, PGDS, PGFS, PGIS, and thromboxane A synthase (TXAS). This review summarizes the biochemical properties, reaction mechanism, and active site details of PG synthases. Because PGs are involved in the immune system, an understanding of PG synthases is important in the design of new anti-inflammatory drugs. The biosynthesis of PGs in various organisms, such as mammals, corals, florideae (a class of red algae), yeast, and fungi, is also introduced. The expression of PG synthases in the microbial systems for the synthesis of PGs is discussed. Now, the biosynthesis of PGs from glucose or glycerol is possible using metabolically engineered cells expressing both unsaturated fatty acid-producing enzymes and PG synthases.

The discovery of the first cyclopropyl lactone-containing marine oxylipin in 1981 revealed a new class of compounds with interesting structural motifs exhibiting different bioactive properties. The development of stereodivergent approaches, structural elucidation strategies, and reassignment of certain configurations represented challenges for natural product researchers and built the fundament on a variety of publications. We herein will summarize the overall investigation on cyclopropyl lactone-containing marine oxylipins. Our focus lays thereby on the well-described constanolactones, solandelactones, and the related halicho- and neohalicholactone. This review embraces the isolation, proposed biosynthesis, characterization, and structural elucidation as well as summarizes investigated attractive (stereo-) selective approaches or methods toward common intermediates by structuring them according to the first applied retrosynthetic disconnection.

Eicosanoids are a family of bioactive lipid mediators that regulate a wide variety of physiological as well as pathological responses and often exhibit potent inflammatory properties. Furthermore, lipid-metabolizing enzymes and rate-limiting steps in lipid-regulating and lipid-producing metabolic cascades have been targeted for drug development. In this chapter, based on a genomic comparison of the arachidonic acid metabolic system in Metazoa, we present a clear overview of the metabolism and eicosanoid signaling in amphioxus through genomic, transcriptomic, and lipidomic approaches. We will discuss evolutionary hypotheses and evidence of the origin of lipid metabolism and how lipid signaling participates in inflammatory responses in this basal chordate.