title: First evidence of a potential antibacterial activity involving a laccase-type enzyme of the phenoloxidase system in Pacific oyster Crassostrea gigas haemocytes.
abstract: Phenoloxidases (POs) are a group of copper proteins including tyrosinase, catecholase and laccase. In several insects and crustaceans, antibacterial substances are produced through the PO cascade, participating in the direct killing of invading microorganisms. However, although POs are widely recognised as an integral part of the invertebrate immune defence system, experimental evidence is lacking that these properties are conserved in molluscs, and more particularly in the Pacific oyster Crassostrea gigas. In the present study, Vibrio splendidus LGP32 and Vibrio aestuarianus 02/041 growths were affected, after being treated with C. gigas haemocyte lysate supernatant (HLS), and either a common substrate of POs, l-3,4-dihydroxyphenylalanine (L-DOPA), to detect catecholase-type PO activity, or a specific substrate of laccase, p-phenylenediamine (PPD), to detect laccase-type PO activity. Interestingly, a higher bacterial growth inhibition was observed in the presence of PPD than in the presence of L-DOPA. These effects were suppressed when the specific PO inhibitor, phenylthiourea (PTU), was added to the medium. Results of the present study suggest, for the first time in a mollusc species, that antibacterial activities of HLS from C. gigas potentially involve POs, and more particularly laccase catalysed reactions.
authors.affiliation: Littoral Environnement et Sociétés (LIENSs), UMR 6250, CNRS-Université de La Rochelle, 2 rue Olympe de Gouges, F-17042 La Rochelle Cedex 01, France. aluna1508@yahoo.com
authors.forename: Andrea
authors.initials: A
authors.lastname: Luna-Acosta
authors.forename: Denis
authors.initials: D
authors.lastname: Saulnier
authors.forename: Mylène
authors.initials: M
authors.lastname: Pommier
authors.forename: Philippe
authors.initials: P
authors.lastname: Haffner
authors.forename: Sophie
authors.initials: S
authors.lastname: De Decker
authors.forename: Tristan
authors.initials: T
authors.lastname: Renault
authors.forename: Hélène
authors.initials: H
authors.lastname: Thomas-Guyon
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D049896:Crassostrea / Q000201:enzymology* / Q000276:immunology; D006434:Hemocytes / Q000201:enzymology*; D007113:Immunity, Innate / Q000276:immunology*; D042845:Laccase / Q000276:immunology* / Q000494:pharmacology; D007980:Levodopa / Q000378:metabolism; D010655:Phenylenediamines / Q000378:metabolism; D010670:Phenylthiourea; D014733:Vibrio / Q000187:drug effects* / Q000254:growth & development
chemical_list: D010655:Phenylenediamines; D007980:Levodopa; D010670:Phenylthiourea; D042845:Laccase; C029728:4-phenylenediamine