A NEW METHOD OF MEASURING GLUCOAMYLASE AC TIVITY

A new method for measuring glucoamylase activity is proposed. In this method, G2-CNP (2-chloro-4 -nitrophenyl a-D-glucopyranosyl-(1-->4)-bet a-D-glucopyranoside) is used as the substrate and the resulting produc t is measured, from which the amount of enzymatic activity is then qua ntitatively determined. This method has the following advantages: (i) The presence of glucose in the sample does not influence the results o f the measurement, and therefore there is no need to dialyze the sampl e prior to analysis. (ii) The presence of alpha-amylase of Aspergillus oryzae in the sample does not affect the results of measurement becau se it cannot hydrolyze the substrate. (iii) The assay procedure is sim ple, and can be easily accomplished in a short time. The proposed meth od showed good correlation with the method generally used for glucoamy lase assay. Coefficients of variation were within 1% in both within-da y and day-to-day experiments. Since alpha-glucosidase can also hydroly ze the substrate, the measurement results showed the sum total of gluc oamylase and alpha-glucosidase activities (that is, glucose forming ac tivity) when alpha-glucosidase was present in the sample. A method for the differential assay of glucoamylase and alpha-glucosidase activiti es in the same sample was also developed.