Department of Biotechnology, Faculty of Agro-Industry, Kasetsart University, Bangkok, Thailand.
Int J Biol Macromol. 2010 Oct 1;47(3):317-24. doi: 10.1016/j.ijbiomac.2010.01.004. Epub 2010 Jan 18.
The enzyme alpha-amylase from Bacillussubtilis was applied to partly hydrolyze purified cassava amylopectin into groups of clusters, which were called domains. The domains were further size-fractionated by methanol precipitation and then subjected to a second stage of alpha-amylolysis until the rate of hydrolysis was slow in order to release the single clusters. All domain and cluster fractions were hydrolyzed with beta-amylase into beta-limit dextrins. The size distribution and chain composition of the beta-limit dextrins were analyzed by gel-permeation chromatography and high-performance anion-exchange chromatography with pulsed amperometric detection, respectively. The sizes of the clusters in the form of beta-limit dextrins were uniform with an average degree of polymerization of 67-78. The distribution profiles of B-chains were similar in all cluster fractions, which suggested that the internal structure of the cassava amylopectin clusters was homogenous. Long B-chains were involved in the interconnection of clusters in the domain fractions. These were cleaved and a new group of chains of intermediate length was produced by the alpha-amylase together with short chains. In the isolated clusters, however, some chains corresponding to long B-chains still remained, which is not predicted by the traditional cluster model of the amylopectin structure. Instead, the alternative two-directional backbone model could explain the mode of interconnection between the clusters.
来自枯草芽孢杆菌的α-淀粉酶被应用于部分水解纯化的木薯支链淀粉，形成一群被称为结构域的簇。这些结构域通过甲醇沉淀进一步进行分级分离，然后进行第二阶段的α-淀粉酶解，直到水解速率变慢，以释放单个簇。所有的结构域和簇级分都用β-淀粉酶水解成β-极限糊精。通过凝胶渗透色谱和高效阴离子交换色谱与脉冲安培检测，分别分析了β-极限糊精的大小分布和链组成。β-极限糊精形式的簇的大小均匀，聚合度为 67-78。所有簇级分的 B-链分布曲线相似，这表明木薯支链淀粉簇的内部结构是均匀的。长 B-链参与了结构域级分中簇的连接。这些链被α-淀粉酶切断，并与短链一起产生新的一组中等长度的链。然而，在分离的簇中，一些对应于长 B-链的链仍然存在，这与支链淀粉结构的传统簇模型不一致。相反，双向骨架模型可以解释簇之间的连接模式。
