The pH is one of the important parameters capable of affect
enzymatic activities in aqueous solution or emulsion. As reported in
Fig. 2, the optimum pH of the olive lipase is 5.0 employing triolein
as substrate. The optimal pH recorded is different from that indicated
by Olías et al. [32] for olive oil acylhydrolase, pH 8.5. This
striking difference suggests the presence of two lipase isoforms,
with different biochemical characteristics, in olive fruit; in fact, the
different extraction systems employed by Olías et al. [32] and us
could have determined the loss of the acidic or the alkaline isoform,
respectively. This is indirectly supported by the fact that oil seed
lipases are characterized by pH optimal spanning, e.g. for castor
bean seedlings, from 4.2 [9] to 9.0 [24]; furthermore, few papers on
fruit lipases reported a pH optimum from acid (4.5) [1] to alkaline
(9.0) [40,31] for oil palm fruit mesocarp lipases, which is particularly
active upon the abscission of the fruit so that 15 min are
sufficient for the hydrolyzation of 40% of the fruit oil [8]. Another
characterized fruit acid lipase (optimum at pH 6) was identified in
crude extract of karanda (Carissa carandas L.) [25].