Abstract
Branching enzyme [α-1, 4-glucan : α-1, 4-glucan 6-glycosyltransferase EC 2.4.1.18] from Bacillus megaterium strain No.10-5 was purified to an enzyme preparation completely free of enzyme contaminants that were capable of modifying the substrates and products of the branching reaction. The molecular weight of the enzyme was determined to be 85, 000 by sucrose density gradient ultracentrifugation. The isoelectric point of the enzyme was pH 4.5. The enzyme was most active at pH 7.6 and 25°C, and stable up to 40t at pH 7.0 and in the range of pH 6.5-8.5 at 25°C in the 2 hr incubation. This enzyme converts amylose, soluble starch and amylopectin into a glycogenlike molecule. The minimum length of maltodextrin chain on which the branching enzyme can act as a substrate was found to be maltononaose. Furthermore, it was shown that the branched dextrin, the substrate of the branching enzyme, had 12 glucose units for its minimum chain length.
