The binding mode of cladocoran A to the human group IIA phospholipase A(2)

Unusual cyclic terpenoids with terminal pendant prenyl moieties: from occurrence to synthesis

The paper reviews the known examples of cyclic terpenoids produced from open chain polyenic precursors by an "unusual" biosynthetic pathway, involving selective electrophilic attack on an internal double bond followed by cyclization. The resulting compounds possess cyclic backbones with pendant terminal prenyl groups. Synthetic approaches applied for the synthesis of such specifically functionalized compounds are also discussed, as well as biological activity of reported representatives.

The inactivation mechanism of human group IIA phospholipase A(2) by Scalaradial

Secretory phospholipases A(2) (sPLA(2)s) are implicated in the pathogenesis of several inflammation diseases, such as rheumatoid arthritis, septic shock, psoriasis, and asthma. Thus, an understanding of their inactivation mechanisms could be useful for the development of new classes of chemical selective inhibitors. In the marine environment, several bioactive terpenoids possess interesting anti-inflammatory activity, often through covalent and/or noncovalent inactivation of sPLA(2). Herein, we report the molecular mechanism of human group IIA phospholipase A(2) (sPLA(2)-IIA) inactivation by Scalaradial (SLD), a marine 1,4-dialdehyde terpenoid isolated from the sponge Cacospongia mollior and endowed with a significant anti-inflammatory profile. Our results have been collected by a combination of biochemical approaches, advanced mass spectrometry, surface plasmon resonance, and molecular modeling. These suggest that SLD acts as a competitive inhibitor. Indeed, the sPLA(2)-IIA inactivation process seems to be driven by the noncovalent recognition process of SLD in the enzyme active site and by chelation of the catalytic calcium ion. In contrast, covalent modification of the enzyme by the SLD dialdehyde moiety emerges as only a minor side event in the ligand-enzyme interaction. These results could be helpful for the rational design of new PLA(2) inhibitors that would be able to selectively target the enzyme active site.

Plakilactones from the marine sponge Plakinastrella mamillaris. Discovery of a new class of marine ligands of peroxisome proliferator-activated receptor γ

In this paper we report the isolation and the molecular characterization of a new class of PPARγ ligands from the marine environment. Biochemical characterization of a library of 13 oxygenated polyketides isolated from the marine sponge Plakinastrella mamillaris allowed the discovery of gracilioether B and plakilactone C as selective PPARγ ligands in transactivation assays. Both agents covalently bind to the PPARγ ligand binding domain through a Michael addition reaction involving a protein cysteine residue and the α,β-unsaturated ketone in their side chains. Additionally, gracilioether C is a noncovalent agonist for PPARγ, and methyl esters 1 and 2 are noncovalent antagonists. Structural requirements for the interaction of these agents within the PPARγ ligand binding domain were obtained by docking analysis. Gracilioether B and plakilactone C regulate the expression of PPARγ-dependent genes in the liver and inhibit the generation of inflammatory mediators by macrophages.