PROPERTIES OF FLAVOBACTERIUM-ODORATUM KU ISOAMYLASE

Isoamylase was purified from the culture filtrate of Flavobacterium od oratum KU to a single protein by starch adsorption and gel-permeation chromatography on a Toyopearl HW-55S column. The molecular weight and isoelectric point of the enzyme were found to be 78000 and 8.7, respec tively. The enzyme was stabilized and stimulated by Ca2+. Its optimum temperatures for activity were 50 and 45 degrees C in the presence and absence of CaCl2 (1 mM), respectively, and the optimum pH was 6.0 in the presence of CaCl2 (1 mM). The enzyme debranched amylopectin and gl ycogen completely The Km and It values of the enzyme for amylopectins and glycogens were similar but were slightly lower than the values for the beta-limit dextrins of these polysaccharides. The k(0) values for the beta-limit dextrins of potato amylopectin and rabbit liver glycog en were slightly lower and higher than those of the mother polysacchar ides, respectively. Pullulan was practically not hydrolyzed. Flavobact erium isoamylase did not hydrolyze (1-->6)-alpha-D-glucosylcyclodextri ns (CDs), and it debranched branched CDs having longer (1-->4)-alpha-g lucan side chains than maltotriosyl residues, and maltosyl CDs with di fficulty. The enzyme practically did not hydrolyze raw starches but ii enhanced the raw-starch digestion of glucoamylases synergistically.