Structures of Multi-Branched Dextrins Produced by Saccharifying α-Amylase from Starch

Abstract

From the digest of beta-limit dextrin (prepared from glutinous rice starch) with saccharifying alpha-amylase of Bacillus subtilis [EC 3.2.1.1] (BSA), two extensibely branched dextrins consisting of nine (No. 6, Fig. 1) and ten (No 7, Fig.1) glucose units were isolated by paper chromatography. Structural analysis using various enzymes revealed that No. 6 and No. 7 were both mixtures of four triply branched dextrins. They had structures which were built up with 63-alpha-glucosylmaltotriose and/or 62-alpha-glucosylmaltose as a linking unit. However, the branching configuration and the minimum alpha-1, 4-glucosidic linkages existing between two branches followed one of the three structures shown below: (see article).

The fine structure of cassava starch amylopectin. Part 2: Building block structure of clusters

“…In sample III, dextrins corresponding to the branched blocks of group 3 at DP 10-15 preponderated. At DP [16][17][18][19], which corresponded to group 4, the chromatograms possessed double or triple peaks at each DP value, suggesting a manifold of multiply branched dextrins. As the elution time simultaneously decreased with increasing branches, exact assignments of the DPs for these peaks were difficult to make.…”

“…e Average inter-block degree of polymerization. f Branched building blocks of group 2 (DP 5-9), 3 (10-15), 4 (16)(17)(18)(19), and 5 (≥20).…”

“…This showed that the blocks of group 3 contained a mixture of both configurations. As the B-chain of the ␣-limit dextrin contains one or two residues on both the nonreducing and the reducing-end side of a branch point [15], and in addition the shortest possible ICL is 1 in amylopectin [16,36], the Cchain of the Staudinger-type blocks have a minimum of 5 residues. In the Haworth-type the C-chain is 3-5 residues (Fig.…”

“…The average CL of the building blocks in potato and amaranth clusters was only ∼4, whereas the internal chain length (ICL) was ∼2 and ∼3, respectively [11,13]. The exact molecular structure of the different blocks was not characterized, but earlier studies on the detailed structure of ␣-limit dextrins obtained from waxy rice amylopectin [14][15][16] give a good opportunity to understand their type of structures. In the potato clusters the building blocks were interconnected through internal chain segments with ICL 7-8 and in amaranth ∼6.8.…”

Fine Structure of Amylopectin

“…They described the structure of singly and multiply branched limit dextrins from waxy rice in great detail and found that, by far, the most prominent dextrins are only singly branched. In LDs with three or more chains, they found that the branches are separated by one or two glucose residues (i.e., ICL is 1 or 2) and that branches never appear next to each other in amylopectin (Umeki and Yamamoto 1975a).…”