Spectrophotometric Assay for Lipase in Serum Using a Chromogenic Substrate, Orange I Laurate

Abstract

A sensitive spectrophotometric method for the assay of lipase in serum is described, based on the use of a chromogenic substrate, Orange I laurate. Orange I liberated from the substrate (used as an emulsion) under the optimal conditions for the enzyme reaction in the presence of sodium cholate (emulsifier of the substrate, activator of lipase, inhibitor of esterases) and sodium dodecyl sulfate (activator of lipase, inhibitor of esterases) is determined spectrophotometrically after adding concentrated sodium cholate to stop the enzyme reaction and to dissolve unreacted substrate, and diluting the mixture with water to reduce the absorbance due to the substrate. Serum lipase activities obtained by this method correlated well with those obtained by a method using olive oil as a substrate. The method is readily performed with good precision, and is suitable for the assay of many samples.