Latex lipase of Euphorbia characias L.: An aspecific acylhydrolase with several isoforms

The objective of the present work was to contribute to the understanding of the physiological role of latex lipolytic activity in Euphorbia characias. To this end, the acid and basic lipolytic activity of E. characias latex, as well as the substrate specificity on various triacylglycerols, were measured during the plant's vegetative and reproductive stages. Both activities appeared to increase during the reproductive stage and to peak at the beginning of the vegetative stage, when new leaves and branches are formed. For the first time, the phospholipolytic and esterase activity of E. characias latex is also reported. An extraction method in aqueous medium with the zwitterionic detergent CHAPS was successfully used to extract lipolytic activity from latex. Extraction permitted the selective recovery of a single protein spot, with a molecular weight of 37 kDa, and presumably made of several acid isoforms which retained both lipolytic and phospholipolytic activity. The biochemical results suggest that lipolytic and phospholipolytic activity could depend on a single hydrolytic enzyme with several isoforms, equally expressed throughout the biological cycle of the plant. On the basis of the obtained results, we hypothesise that the E. characias latex lipase should be considered as an aspecific acylhydrolase with a combined lipase/phospholipase A activity.