Purification and physiocochemical properties of an extra-cellular cycloamylose (cyclodextrin) glucanotransferase from...

An extracellular cycloamylose (cyclodextrin) glucanotransferase (EC 2.4.1.19) from Bacillus macerans was purified to homogeneity by adsorption on starch, ammonium sulfate fractionation, column chromatography on DEAE-cellulose, and gel filtration on Sephadex G-100. The enzyme had a molecular weight of 67,000 and consisted of one polypeptide chain. The isoelectric point was pH 5.4. Temperature and pH optima were 60 degrees and 5.4--5.8, respectively. The purified enzyme was quite stable at 50 degrees (pH 6.0), but lost approximately 80% of its activity at 60 degrees for 30 min (pH 6.0). Prolonged digestion by trypsin did not affect the catalytic properties of the enzyme. The Km for starch was 5.7 mg/ml.