Determinants for the specificity of action of pancreatic lipase

Abstract

A number of chromogenic fatty acid esters were prepared and studied as substrates for pancreatic lipase and hepatic esterase in an attempt to elucidate the factors involved in differentiating pancreatic lipase from other esterolytic enzymes. It was shown that specificity of a substrate for lipase is dependent not only upon the acyl chain length but also upon the number of ester groups present in the substrate. It is suggested that the structure of the lipide-water interface of the emulsions formed by these esters is correlated in a regular manner with their chemical structure and acts as an additional determinant of specificity for lipase by offering steric hindrance to aliesterase. The measurement of lipase in the presence of large amounts of other esterases requires the use of a substrate system of relatively high specificity. Tributyrin, which is in wide use for the measurement of human “serum lipase,” does not fulfil the criteria for a high degree of specificity. Although chromogenic substrates of greater specificity for lipase than 2-naphthyl laurate were demonstrated, a more sensitive colorimetric method for serum lipase was not evolved.