Abstract
In a previous study, we prepared phosphoryl oligosaccharides (POs) from potato starch hydrolysate and investigated their inhibitory effect on the formation of a calcium phosphate precipitate. In this study, we investigated the enhancement of the inhibitory effect using the coupling reaction of cyclomaltodextrin glucanotransferase (CGTase) (EC 2.4.1.19). In this treatment, the effect of the POs was obviously improved and conversion of the PO structure was observed. By the coupling reaction of CGTase, the fraction of POs with one phosphoryl group decreased, and the fraction with at least two phosphoryl groups increased to 33% from 10%. Phosphoryl maltopentaose was the main substrate for the coupling reaction of the enzyme. The products (CGT-POs) obtained after CGTase reaction were fractionated by ion-exchange chromatography into three fractions, CGT-PO1, CGT-P02a, and CGT-P02b. The fractions of CGT-P02a and CGT-P02b were the main components of the CGT-POs having an inhibitory effect on calcium phosphate formation. The fraction CGT-P02a was maltooligosaccharide with an average degree of polymerization (DP) of 7.89, to which two phosphoryl groups were attached. The fraction CGT-P02b was maltooligosaccharide with an average DP of 11.06, to which three phosphoryl groups were attached. In addition, the fraction CGT-P02b was more effective than fraction CGT-P02a since the threshold value of the concentration of CGT-P02b to exhibit the inhibitory effect was 7-fold lower than that of CGT-P02a.
