In conclusion, an acid lipase activitywas detected in the oil body
fraction of mesocarp olive fruit suggesting that such lipase is closely
associated with oil droplets. The physiological role of lipase in
seedlings was well characterized [17], whilst the role of lipase in
fruits is still unclear. The data obtained allowed to reveal the
presence of an acid lipase in olive oil mesocarp, albeit with low
catalytic activity. In fact, the mesocarp olive lipase activity is very
low if compared with the acid lipase activity of castor bean seed
(5.4 0.3 nmol oleic acid min1 mg1 protein) as indicated by
Eastmond [9]. This is probably linked to lipase localization and to its
physiological roles in TAGs metabolism. In oil seeds oleosins not
only facilitate the anchorage of lipase to the oil body, regulating the
metabolism of TAGs [18], but they also prevent the coalescence of
oil bodies during seed desiccation, thereby maintaining the large
surface to volume ratio required for rapid metabolism of TAG
during germination [30]. Instead, in oily fruits as olives, because of
the absence of oleosins, the presence of large oil globules limits the
action of lipase reducing the accessibility of the TAG substrates.