Fluorometric method for measuring serum lipase activity.

We describe a method for determining lipase (triacylglycerol acyl-hydrolase, EC 3.1.1.3) activity in serum. Emulsified olive oil in tris(hydroxymethyl)aminomethane buffer is used as substrate. The course of the enzymatic reaction is followed by measuring the decrease in fluorescence with time of a fluorescent indicator, 4-methylumbelliferone, added to the substrate, caused by the change in the pH of the substrate solution resulting from the reaction. All measurements are performed at 37 degrees C. The reaction volume is about 2.3 ml, in a Pyrex cuvette. Change of fluorescence and of enzyme activity are linearly related in the range of 77.8 to 389.0 U/liter. An assay can be done in as little as 3 to 5 min, with excellent precision.