Department of Biochemical Science and Technology, Faculty of Agriculture, Kagoshima University

Abstract

The fluorescent labeling/HPSEC method, which is capable of direct determination of a molar distribution, was applied to structural characterization of the product from amylose by starch branching enzyme(SBE) from potato (Solanum tuberosum L.) tubers. The SBE product, excluding possible cyclic molecules, wasa mixture of branched and linear molecules with molar proportions of 65 and 35%, respectively. Size distribution of the product on a molar basis showed three distinct populations at degree of polymerization (DP) of1190, 30 and 7-6, which suggested branched, linear/branched, and linear molecules, respectively. The debranched SBE products exhibited periodicity with intervals of -6, that is, peaks at DP 6, 11, 18 and 29, which implies a helical turn being a unit-structure for SBE action. C-chain of branched molecules of the SBEproduct showed a narrow DP distribution (30-50) which was distinct from that of native amylopectin.