Characterization of glucoamylase from Lactobacillus amylovorus ATCC 33621

An intracellular glucoamylase, purified from Lactobacillus amylovorus, reacted selectively with polysaccharides. Kinetic studies indicated low affinity for maltose and maltotriose (K-m 58 g/ml and 178 g/ml) and higher affinity for starch and dextrin (K-m 0.01 g/ml and 0.02 g/ml). Glucoamylase was inhibited almost 50% by 10 mM glucose. Cu2+ and Pb2+ inhibited glucoamylase at 1.0 mM but EDTA and other metal chelators had no effect on the enzyme activity. Acarbose and Tris inhibited the enzyme by 84% and 98%, respectively at 1 mM, while iodoacetate and p-chloromecuribenzoic acid inhibited activity by 98% and 78%, respectively at 10 mM. The purified enzyme was thermolabile at temperatures greater than 55 degrees C and thus has potential for application in the brewing industry.