Kozo Komae

Improvement of a method for chain-length distribution analysis of wheat amylopectin

For the chain-length distribution analysis of wheat amylopectin using high-performance anion-exchange chromatography (HPAEC) under alkaline conditions, the reduction of amylopectin isoamylolyzate with sodium borohydride facilitated obtaining reproducible chromatograms without both alkaline degradation and epimerization of maltooligosaccharides in aqueous NaOH solution. In a comparison of the chromatograms of isoamylolyzates of wheat starch and its fractionated amylopectin, reproducible results were also obtained. The improved method presented here, based on the use of starch isoamylolyzates reduced with sodium borohydride, is available for performing automated analysis of the chain-length distribution of wheat amylopectin by HPAEC equipped with an autosampler.

New Sweet Potato Line having low Gelatinization Temperature and altered Starch Structure

A new sweet potato breeding line, Kanto 116, was developed, featuring low gelatinization temperature and an altered starch fine structure. Starch granules from Kanto 116 showed an abnormal morphology characterized by cracking into granules. Starch content, amylose content and tuberous root appearance of Kanto 116 were similar to those of the control and the parents. Pasting temperatures of Kanto 116 starch determined by the Rapid Visco Analyser were 51.4 - 52.6 °C, approximately 20 °C lower than those of the control and parents starches. Onset, peak, and conclusion temperature of gelatinization, and gelatinization enthalpy of Kanto 116 starch determined by differential scanning calorimetry were 39.0 °C, 46.9 °C, 64.8 °C, and 8.8 J/g, respectively, and much lower than those of the control and parents starches. The chain-length distribution of the amylopectin molecules, determined by high-performance anion-exchange chromatography, showed that Kanto 116 starch had a higher proportion of short chains (DP 6 - 11) and a lower proportion of chains between DP 12 - 28 than control and parent starches. The debranched β-limit dextrin of Kanto 116 starch also showed that the proportion of both short and long B1 chains was different from those of the control and parents starches.

Varietal differences and chromosome locations of multiple isoforms of starch branching enzyme in wheat endosperm

Abstract Starch branching enzyme isolated from wheat endosperm was fractionated into two distinct isoforms, BE I and BE II, using anion-exchange column chromatography on Q-Sepharose Fast Flow. Both BE I and BE II were separated precisely into several isoforms using native polyacrylamide electrophoresis coupled with enzyme activity staining, and varietal differences in the major BE I isoforms expressed in the endosperm 21 days after flowering were observed. Chromosome locations of genes controlling the expression of the three BE I isoforms of ‘Chinese Spring’ were determined using aneuploid analysis, which indicated that two isoforms, BE I-1 and BE I-2, are controlled by 1DL and the other isoform, BE I-4, is 7BL.