INTERFERENCE OF CYCLODEXTRINS WITH AMYLOLYTIC ACTIVITY ASSAYS OF CYCLODEXTRIN GLYCOSYLTRANSFERASES

Cyclodextrin glycosyltransferases (CGTases) catalyse the cyclisation o f starch dextrins to cyclodextrins and concomitantly show amylolytic a ctivity which is commonly determined by the starch-iodine assay. In th e present study it was found that cyclodextrins interfere with this as say. Adding cyclodextrins in concentrations ranging from 0.01mM to 0.6 mM to starch-iodine complex solution resulted in a significant decreas e in absorbance at 600nm due to alpha- and beta-cyclodextrin competing with starch in the iodine complex formation. The largest reduction wa s caused by alpha-cyclodextrin. Therefore, the use of the starch-iodin e assay will result in an overestimation of the amylolytic activity of CGTases-particularly when the enzyme has a high alpha-cyclodextrin pr oduction activity. In contrast, determination of the amylolytic activi ty by measurement of released reducing sugars with CuSO4/bicinchonate was not disturbed by cyclodextrins.