Kong Xiangli, Corke Harold, Bertoft Eric
School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China.
Carbohydr Res. 2009 Sep 8;344(13):1701-8. doi: 10.1016/j.carres.2009.05.032. Epub 2009 Jun 17.
The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with alpha-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then beta-amylase to remove all external chains, whereby the internal structure was obtained. The phi,beta-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC-PAD). The results showed that the domain fraction contained approximately 2.2 clusters, and single clusters were composed of approximately 13 chains. The phi,beta-limit dextrins of the clusters were further hydrolyzed with alpha-amylase to characterize their building block composition. The average DP of the branched blocks was approximately 11 and they contained on average approximately 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of approximately 6 branched blocks, and the internal chain length between the blocks was approximately 6.8.
本研究的目的是确定苋属谷物支链淀粉的精细结构。苋属支链淀粉用α-淀粉酶水解，通过甲醇沉淀分离出单簇和一组簇（结构域）。对结构域和簇用磷酸化酶a处理，然后用β-淀粉酶处理以去除所有外链，从而获得内部结构。在琼脂糖CL 6B上分析φ，β-极限糊精。簇级分的平均聚合度（DP）和峰值DP值分别为57和82；结构域的值分别为137和309。通过带脉冲安培检测器的高效阴离子交换色谱法（HPAEC-PAD）分析单位链长分布。结果表明，结构域级分包含约2.2个簇，单簇由约13条链组成。簇的φ，β-极限糊精用α-淀粉酶进一步水解以表征其结构单元组成。分支结构单元的平均DP约为11，平均包含约2.5条链。它们的平均链长、内部链长和分支度分别约为4.3、2.8和14。一个簇由约6个分支结构单元组成，结构单元之间的内部链长约为6.8。
