A simultaneous-coupling azo dye method for the quantitative assay of esterase using alpha-naphthyl acetate as substrate

Summary This paper describes a simultaneous-couplng azo dye method for the measurement of estarase activity using the histochemical substrate, -naphthyl acetate. By the choice of two diazonism salts with optimal coupling characteristics, the reaction be carried out at any pH between 3.0 and 9.5. The azo dye is maintained in solution for spectrophotometric measurements with bovine serum albumin. The simultaneous-coupling method is compared with an assay based on the direct measurement of released -naphthol by its ultra-violet bsorbance in a pH study of hog liver esterase. There is good agreement between the data obrained by both methods.