Hydrolysis of 4‐methylumbelliferyl butyrate: A convenient and sensitive fluorescent assay for lipase activity

Abstract

Abstract A rapid, sensitive and convenient fluorescent assay was developed to screen for lipase activity. The non‐fluorescent substrate, 4‐methylumbelliferyl butyrate (4‐MUB), solubilized in either liposomal dispersions or bile salt/lecithin mixed micelles, is hydrolyzed to butyric acid and the highly fluorescent compound, 4‐methylumbelliferone (4‐MU). Assays are run at 37 C for 10 min, terminated, and the changes in fluorescence quantitated with a Turner III fluorometer. Both lingual and pancreatic lipases exhibit activity against this artificial substrate. The assay has several advantages: nmoles 4 MU/ml/hr are measured allowing the detection of very low lipolytic activity; multiple samples may be simultaneously assayed, and only a brief incubation period is required.