Bioactive long chain N-acylethanolamines in five species of edible bivalve molluscs. Possible implications for mollusc physiology and sea food industry.

ABSTRACT

Several long chain N-acylethanolamines, including the proposed endogenous ligands of cannabinoid receptors, anandamide (N-arachidonoylethanolamine, C204 NAE) and N-palmitoylethanolamine (C160 NAE), as well as some of their putative biosynthetic precursors, the N-acyl-phosphatidylethanolamines, were found in lipid extracts of five species of bivalve molluscs, including Mytilus galloprovincialis, commonly used as sea food. The amounts of these metabolites, the most abundant being C160 NAE and N-stearoylethanolamine, appeared to increase considerably when mussels were extracted 24h post-mortem, but were not significantly affected by boiling the tissue prior to extraction. In particulate fractions of homogenates from Mytilus, where the existence of a highly selective cannabinoid receptor with an immunomodulatory function has been previously described, an enzymatic activity capable of catalyzing the hydrolysis of C204 NAE amide bond, and displaying similar pH dependency and inhibitor sensitivity profiles as the recently characterized 'fatty acid amide hydrolase' was found. The enzyme Km and Vmax for C204 NAE were 29.6 microM and 73 pmol/mg protein/min, respectively. These findings support the hypothesis that C204 NAE, never reported before in the phylum Mollusca, may be a mollusc physiological mediator, and suggest that edible bivalves may be a dietary, albeit limited, source of C160 NAE, whose anti-inflammatory properties, when administered orally in amounts higher than those reported here, have been previously reported.