[Determination of lipase with 8-phenyloctanoic acid vinyl ester as the substrate]

The UV-test described by Myrick ((1976) Ph. D. Thesis, Birmingham, AL, USA) for the determination of the catalytic activity of lipase in serum, using 8-phenyloctanoic acid vinyl ester as substrate, was investigated in detail. When tested with sera the assay gave unsatisfactory linearity. For some serum samples, evaluation was impossible, owing to the complete lack of a linear response. The substrate is attacked not only by purified pancreatic lipase, but also by liver esterase, cholinesterase in plasma, and lipoproteinlipase. Attempts to inhibit the interfering esterases with phenylmethylsulphonylfluoride were unsuccessful. Analyses of 102 sera showed no correlation with the results from the titrimetric assay (r = 0.158). Thus the method of Myrick does not provide clinically useful results.