title: Further insights on the structural aspects of PLA(2) inhibition by gamma-hydroxybutenolide-containing natural products: a comparative study on petrosaspongiolides M-R.
abstract: Petrosaspongiolides M-R (PM-PR, 1-5) are marine sesterterpenes structurally characterised by a gamma-hydroxybutenolide moiety. They have shown an in vitro and in vivo potent anti-inflammatory activity, mediated by specific inhibition of secretory phospholipase A(2) (sPLA(2) enzymes). The molecular mechanism underlying the sub-micromolar irreversible inhibition of the bee-venom PLA(2) (bvPLA(2)) by PM has been clarified combining mass spectrometry (MS) and molecular modelling approaches. The N-terminal amino group (Ile-1 residue), recently identified as the unique PM covalent binding site on this enzyme, selectively delivers a nucleophilic attack onto the masked aldehyde at C-25 of the pharmacophoric gamma-hydroxybutenolide ring of PM, giving rise to a Schiff base. In the attempt of broadening the knowledge of the mechanism at molecular level of PLA(2) inactivation by this family of compounds, we performed a comparative analysis on petrosaspongiolides M-R, whose results are discussed in this paper. Firstly, the amount of bvPLA(2) enzyme covalently modified after incubation with each of petrosaspongiolides M-R was measured and resulted to be in good agreement with pharmacological in vitro data. Then, a full characterisation of the bvPLA(2) adduct with PR, one of the least active and most structurally different among petrosaspongiolides, by LC-MS, MS(n), and computational methods, confirmed the same inhibition mechanism and covalent binding site already found for PM. Finally, extensive molecular docking studies performed in comparison on the PM-PLA(2) and PR-PLA(2) complexes provided critical insight on how the balance between non-covalent and covalent inhibitor-enzyme interactions may affect the final potency exhibited by the various compounds of the petrosaspongiolide family.
authors.affiliation: Dipartimento di Scienze Farmaceutiche, Università di Salerno, via Ponte Don Melillo, 84084, Fisciano (SA), Italy.
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Monti
authors.forename: Agostino
authors.initials: A
authors.lastname: Casapullo
authors.forename: Raffaele
authors.initials: R
authors.lastname: Riccio
authors.forename: Luigi
authors.initials: L
authors.lastname: Gomez-Paloma
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives; D000818:Animals; D001514:Bee Venoms / Q000201:enzymology*; D001665:Binding Sites; D001688:Biological Products; D002851:Chromatography, High Pressure Liquid; D019295:Computational Biology; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D005663:Furans / Q000737:chemistry* / Q000494:pharmacology; D007166:Immunosuppressive Agents / Q000737:chemistry / Q000494:pharmacology; D013058:Mass Spectrometry; D008958:Models, Molecular; D015394:Molecular Structure; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors* / Q000737:chemistry
chemical_list: D001514:Bee Venoms; D001688:Biological Products; D004791:Enzyme Inhibitors; D005663:Furans; D007166:Immunosuppressive Agents; C118309:petrosaspongiolide m; D009828:Oleanolic Acid; C004511:butenolide; D010741:Phospholipases A; D015107:4-Butyrolactone