The Enzymatic Action Of 3 Glucoamylase Isoenzymes From Aspergillus-Niger On Different Substrates

Glucoamylase (E.C.3.2.1.3.) can be isolated from different microorganisms. The analytical characteristics of glucoamylase have been frequently described in literature. A direct connection between the kind of producing microorganism and the number of protein bands do not exist. Both the number and the activity of isoenzymes are fundamentally influenced by medium composition, condition of growth and purification procedure.In the paper presented a glucoamylase complex from Aspergillus niger has been separated by SDS-polyacrylamid gel electrophoresis according to Laemmli. It has shown that 2 % SDS in a 0.1 % enzyme solution causes only a small decrease in activity, and consequently the SDS-PAGE can be used for the separation of glucoamylase B with following determination of activity. The rel. molecule mass of the three subunits (GA I, GA II, GA III) was found to be 78 500, 70 800 and 42 000, respectively. All the three subunits catalyse the hydrolysis of polymeric substrates (soluble Zulkowski-starch, SHP and potatoe starch) and D-maltose. Therefore, they are glucoamylases. GA I shows the lowest and GA II the highest enzyme activity. D-maltose is virtually subjected to continuous enzymatic hydrolysis dependent on the glucoamylase isoenzymes.