Lipolytic enzymes of the human pancreas. I. A highly sensitive, specific, and simple measurement of cholesterol ester hydrolase activity.

Cholesterol ester hydrolase (cholesterol esterase, EC 3.1.1.13) does not only act on cholesterol esters, but also on esters of fluorescein. Diesters as well as monoesters of this dye show neither color nor fluorescence, so that these compounds may be used as chromogenic or fluorogenic substrates. Splitting off the ester bonds immediately causes the return of the original properties of the fluorescein. Its dilaurate was found to be a specific substrate of cholesterol esterase, allowing the measurement of activities of this enzyme down to ranges of 0.01 U/1 by a fluorometric assay.