Oxidation of cinnamyl alcohol and ethanol by oxidases and dehydrogenases in the digestive gland of gastropods

Alcohol oxidases and dehydrogenases are poorly studied in the Mollusca, the second largest phylum of metazoans. In order to obtain an overview of the distribution of aromatic alcohols and ethanol-oxidizing enzymes in the gastropod phylogenetic tree, we investigated the activity of these enzymes in the digestive gland of 26 gastropod species in the clades Patellogastropoda, Neritimorpha, Vetigastropoda, Caenogastropoda and Heterobranchia. Marine, freshwater and terrestrial species, as well as herbivores and carnivores, were sampled so that gastropods varying widely in habitat and diet were included in the study. An aromatic alcohol oxidase, which was previously reported in herbivorous terrestrial gastropods, was detected in 25 of the studied species. The activity of a cinnamyl alcohol dehydrogenase was detected for the first time in gastropods and this enzyme was found to be present in all the species that were studied. Our study, thus, demonstrates that alcohol oxidases and dehydrogenases are ubiquitous enzymes among gastropods; these enzymes are found across the gastropod phylogenetic tree and across species varying widely in habitat and diet. The enzymes that catalyze the oxidation or dehydrogenation of cinnamyl alcohol must be involved in the metabolism of aromatic alcohols of very different dietary origins and conceivably have a detoxification function. Oxidase or dehydrogenase activities involving ethanol as a substrate were detected only in a few species, mostly those belonging to the Panpulmonata. This suggests that for many gastropods ethanol may not be metabolically relevant.