Cyclomaltodextrin glucotransferases from thermophilic actinomycetes

Cyclomaltodextrin glucotransferases (CGTases, EC 2.4.1.19) were identified in strains of thermophilic actinomycetes for the first time. The enzymes were purified to homogeneity using adsorption on a mixed alpha-and beta-cyclodextrin (CD) polymer followed by ion-exchange and gel-permeation chromatography. Optimal conditions for the catalytic activity of the enzymes (pH 6-7, 50-60 degrees C) were determined. For the CGTases from strains INMIA-A-554 and INMIA-A-561, respectively, the K-m values were 5.0 and 3.33 mg/ml (with starch) and the V-max values were 10.0 and 6.67 mg/min. The substrate and acceptor specificities of the enzymes were studied. The presence of CGTases in thermophilic actinomycetes points to their phylogenetic relationship to aerobic spore-forming bacteria.