Abstract
The action of cyclodextrin glucanotransferase (CGTase: EC 2.4.1.19) on pullulan was examined. A poor susceptibility of CGTase to pullulan was enhanced by increasing the substrate and enzyme concentrations. In spite of a small increase in reducing sugar, large changes in the molecular size of pullulan were observed especially in high-molecular weight pullulan PF30 (Mw 283, 000). These results indicated that a disproportionation activity of CGTase worked predominantly for the reconstruction of pullulan. The product pullulans showed different responses from pullulan when the interaction with the fluorescent reagent and hydrolysis with isoamylase and glucoamylase were compared. Structural analyses of product pullulans by two-dimensional NMR, HMQC, and methylation indicated that CGTase introduced a-1, 4-branch points at the nonreducing side of maltotriosyl units in pullulan molecule yielding, just like α-1, 6-branch points on the linear back bones of α-1, 4-linkages.
