New insights into the action mode of amylosucrase on amylopectin

To investigate the action mode of amylosucrase (AS) on amylopectin, waxy corn starch (WCS) was selected as an acceptor. The effects of WCS dissolution method, reaction temperature, sucrose concentration and AS activity on transglycosylation degree (TD) were investigated. Under the selected reaction condition, the enzymatic reaction process was divided into two stages, i.e. before and after 0.25 h, of which the relations between TD value and reaction time were successfully described using a linear and a logarithmic function, respectively. Then, the elongated WCSs with different TDs were produced according to the theoretical reaction time calculated based on the regression equations. The chain length distribution of the elongated WCSs indicated that all of the branch chains of WCS were greatly elongated by AS before occurrence of starch precipitation. Afterwards, however, AS merely elongated the branch chains whose non-reducing ends were exposed on the surface of the precipitate.