Photometric Microdetermination of Serum Lipase with a Phenyl Laurate Substrate

The Raderecht and Moskau procedure for pancreatic lipase (6) has been modified for determining the small amounts of this enzyme present in normal blood serum. The present investigation confirmed their findings: that phenyl laurate provides a stable easily-prepared substrate of uniform composition; that the substrate is specifically split by serum and pancreatic lipase; and that the reaction product (phenol) can be readily determined by a simple and sensitive colorimetric pro-cedure. The lipase units are expressed in the same manner as are phosphataseunits; i.e., milligramsof phenol liberated per 100 ml. serum at 370 in 30 mm. The normal range, basedon 40 sera, was found to be 2.5-5.6 units. The serum lipase valueswere shown to be significantly elevated in a number of caseswith acute pancreatic disease. The advantage of this procedure over others presently employed for diagnosticevaluation of these conditions is discussed. I N A REVIEW ARTICLE dealing with the fat-splitting enzymes in blood, Overbeek (1) concluded that: “The situation with regard to knowl-edge of these enzymes is thus one of confusion and uncertainty. It is clear that development of standard methods of determination of the various enzymes is very much needed. ” This statement agrees with Lagerlof’s view (2) that the diagnostic importance of serum levels of pancreatic lipase has been doubtful for some time because of the problems in its determination. According to the classification scheme of Richter and Croft (3), the serum lipases are classified with esterases, which hydrolyze fats