Purification and Properties of Cyclodextrin Glycosyltransferase of an Alkalophilic Bacillus sp.

Extracellular cyclodextrin glycosyltransferase (α-1,4-glucan 4-glycosyltransferase, cyclizing, EC 3.2.1.19) of an alkalophilic Bacillus sp. (ATCC 21783) was purified about 74-fold and shown to be a single, homogeneous protein by disc polyacryl amide gel electrophoresis and ultracentrifugation. The molecular weight and isoelectric point were 88,000 and pH 5.4. The optimum pH for the enzyme action was 4.5-4.7. The apparent V_max and Km values for α-, β- and γ-cyclodextrin at the constant concentration of sucrose were 133.3, 23.4, 12.3 µmoles glucose/min per mg protein and 5.88, 0.39, 0.25 mm, respectively. The enzyme converted about 73% of starch, 65% of amylopectin, 45% of glycogen and 25% of amylopectin (β-limit dextrin to cyclodextrins.