Chen_1990_Biochim.Biophys.Acta_1044_111

Fish oil chylomicrons, obtained from mesenteric duct chyle of rats fed [3H]20:5 and [14C]20:4 or [3H]20:5 and [14C]18:2 in a fish oil emulsion, were incubated with human pancreatic lipase-colipase, human carboxyl ester lipase (CEL) and human duodenal contents. With duodenal contents, the triacylglycerols labelled with [3H]20:5 and [14C]20:4 were rapidly converted to free fatty acids (FFA) and monoacylglycerols. Also during incubation with lipase-colipase the [3H]- and [14C]triacylglycerols disappeared completely and at equal rates, but in this case much [3H]20:5 and [14C]20:4 accumulated in diacylglycerols. When CEL was also added, the rate of disappearance of [3H]- and [14C]triacylglycerols increased and the radioactivity of diacylglycerols decreased markedly. During incubation of chylomicrons labelled with [3H]20:5 and [14C]18:2 with lipase-colipase, the rates of hydrolysis of [3H]- and [14C]triacylglycerols were similar, but more [3H]20:5 than [14C]18:2 accumulated in diacylglycerols. The accumulation of [3H]diacylglycerol was reduced by adding CEL. Also when fatty acids were analyzed by gas chromatography, 20:5 was enriched in remaining triacylglycerol and in diacylglycerol after incubation with lipase-colipase alone. The data thus indicate that both lipase-colipase and CEL participate in the hydrolysis of 20:5 and 20:4 ester bonds of dietary triacylglycerol.