Characterization of triacylglycerol lipase activity in human amniotic fluid

A radiochemical assay was used to measure the triacylglycerol lipase activity found in normal human amniotic fluid at term. Enzyme activity was characterized in a partially purified extract of amniotic fluid and was found to be optimal at pH 8.0 +/- 0.2 in the presence of 5mM sodium taurocholate, with the use of emulsified tri-[3H]oleoyl glycerol as the substrate. The assay described made it possible to determine the lipase activity in as little as 25 microliters of a 12,000 x g supernatent of whole amniotic fluid as the source of enzyme. The lipase appeared to be distinct from another triacylglycerol lipase measurable in fetal membranes. In turn, it was shown that the amniotic fluid enzyme exhibited several catalytic properties which resembled those of pancreatic lipase. i.e., its substrate specificity, the bimodal effect of bile salt, and the influence of authentic pancreatic colipase on the catalytic process. The results suggest that the assay of triacylglycerol lipase activity may be clinically useful in the detection of enzyme abnormalities in human amniotic fluid.