Structure and properties of amylopectin isolated from endosperm starch of low-amylose bread wheat

从具有共同遗传背景的近等基因糯性和非糯性小麦品系及低直链淀粉突变体品系中分离到大A型胚乳淀粉粒。A型淀粉的直链淀粉含量在2.6%~ 23.6%之间。用刀豆球蛋白A（Con A）沉淀法从分离的淀粉中分离支链淀粉。碘<max>-支链淀粉复合物在680 nm处的λ_和蓝色值在分离的支链淀粉之间没有显著差异，表明来自非蜡质和低直链淀粉系的支链淀粉不包含影响碘复合物性质的直链淀粉或超长支链淀粉链。通过高效尺寸排阻色谱法（HPSEC）和高效阴离子交换色谱法（HPAEC）测量的链长分布曲线表明，这些品系的支链淀粉结构彼此难以区分。通过HPSEC测量，在支链淀粉中未检测到超长链。Wx-D1基因座上的GBSS I合成等位基因Wx-D1 a、Wx-D1 d、Wx-D1 f和Wx-D1 g对碘-支链淀粉复合物的性质和支链淀粉的链长分布没有影响。

Large A-type endosperm starch granules were isolated from near-isogenic waxy and non-waxy lines and low-amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A-type starch ranged from 2.6% to 23.6%. Amylopectin was isolated by concanavalin A (Con A) precipitation from the isolated starch. The λ_<max> and blue values at 680 nm of the iodine-amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non-waxy and low-amylose lines did not contain such long chains as amylose or extra-long chains of amylopectin affecting iodine complex properties. Chain-length distribution profiles measured by both high-performance size exclusion chromatography (HPSEC) and high-performance anion-exchange chromatography (HPAEC) showed that the amylopectin structure of these lines was indistinguishable from each other. Extra-long chains were not detected in the amylopectins by HPSEC measurement. The alleles on the Wx-D1 locus, i.e. Wx-D1a, Wx-D1d, Wx-D1f, and Wx-D1g, responsible for granule-bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine-amylopectin complex and the chain-length distribution profiles of amylopectin.