Structural Characterization of Amylopectin and Intermediate Material in Amylomaize Starch Granules
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概要
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The fine structures of amylopectin and intermediate material characteristic of amylomaize starch were investigated by chemical and enzymatic means. In comparison with waxy-maize amylopectin, that of amylomaize starch was found to possess a CLapproximately 10 glucose units longer. Unit-chain profiles of waxy and amylomaize amylopectins revealed that the clear difference lay simply in the relative amounts of two unit-chain fractions. By fractionations of debranched /Mimit dextrins, it was demonstrated that the CL of the internal chains in amylomaize amylopectin was 9 glucose units longer than that in waxy-maize amylopectin. In addition, the proportion of maltose and maltotriose fractions in the debranched dextrin for amylomaize amylopectin was noticeably smaller than found for waxy-maize amylopectin. These data suggest a lesser branching frequency of outer branches in amylomaize amylopectin, confirming the previous proposal that this amylopectin has longer inner and outer branches than those of normal amylopectin. As for amylomaize intermediate material, the average degree of polymerization was estimated to be 250 to 300 glucose units per molecule. It was also indicated that there were 5 or 6 glucose residues corresponding to the non-reducing end in the molecule. The unit-chain profile of the intermediate material implied that this molecule was mainly composed of branches with CL around 50. Moreover, the presence of only small amounts of maltose and maltotriose fractions was demonstrated by the unit-chain distribution of this β-limit dextrin. These findings indicate that amylomaize intermediate material is totally consistent with a branched glucan having a low molecular weight, proposing that this anomalous glucan has such a fine structure that four or five branches with CLaround 50 are linked to a main linear chain of 100 to 150 glucose units.
- 社団法人 日本農芸化学会の論文
著者
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BABA Tadashi
Laboratory of Metabolic Chemistry, Institute of Applied Biochemistry, University of Tsukuba
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ARAI Yuji
Laboratory of Metabolic Chemistry, Institute of Applied Biochemistry, University of Tsukuba