Zhu Fan, Bertoft Eric, Szydlowski Nicolas, d'Hulst Christophe, Seetharaman Koushik
School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN, USA.
Carbohydr Res. 2015 Jan 12;401:96-108. doi: 10.1016/j.carres.2014.09.011. Epub 2014 Nov 15.
This is the first report on the cluster structure of transitory starch from Arabidopsis leaves. In addition to wild type, the molecular structures of leaf starch from mutants deficient in starch synthases (SS) including single enzyme mutants ss1-, ss2-, or ss3-, and also double mutants ss1-ss2- and ss1-ss3- were characterized. The mutations resulted in increased amylose content. Clusters from whole starch were isolated by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens. The clusters were then further hydrolyzed with concentrated α-amylase of B. amyloliquefaciens to produce building blocks (α-limit dextrins). Structures of the clusters and their building blocks were characterized by chromatography of samples before and after debranching treatment. While the mutations increased the size of clusters, the reasons were different as reflected by the composition of their unit chains and building blocks. In general, all mutants contained more of a-chains that preferentially increased the number of small building blocks with only two chains. The clusters of the double mutant ss1-ss3- were very large and possessed also more of large building blocks with four or more chains. The results from transitory starch are compared with those from agriculturally important crops in the context that to what extent the Arabidopsis can be a true biotechnological reflection for starch modifications through genetic means.
这是关于拟南芥叶片瞬时淀粉簇结构的首份报告。除野生型外，还对淀粉合酶（SS）缺陷型突变体叶片淀粉的分子结构进行了表征，包括单酶突变体ss1 -、ss2 -或ss3 -，以及双突变体ss1 - ss2 -和ss1 - ss3 -。这些突变导致直链淀粉含量增加。通过使用解淀粉芽孢杆菌的α -淀粉酶进行部分水解，从全淀粉中分离出簇。然后用解淀粉芽孢杆菌的浓缩α -淀粉酶进一步水解这些簇，以产生构建块（α -极限糊精）。通过对脱支处理前后样品的色谱分析来表征簇及其构建块的结构。虽然这些突变增加了簇的大小，但从其单位链和构建块的组成可以看出原因有所不同。一般来说，所有突变体都含有更多的α链，这些α链优先增加了仅含两条链的小构建块的数量。双突变体ss1 - ss3 -的簇非常大，并且还含有更多含四条或更多链的大构建块。在拟南芥在多大程度上可以成为通过基因手段进行淀粉修饰的真正生物技术反映这一背景下，将瞬时淀粉的结果与农业重要作物的结果进行了比较。
