School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland 1142, New Zealand.
J Agric Food Chem. 2013 Oct 16;61(41):9899-907. doi: 10.1021/jf402090f. Epub 2013 Oct 4.
Molecular structures of starches from dull1 maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were characterized and compared with the wild type. Amylose content with altered structure was higher in the nonwaxy mutants (25.4-30.2%) compared to the wild type maize (21.5%) as revealed by gel permeation chromatography. Superlong chains of the amylopectin component were found in all nonwaxy samples. Unit chain length distribution of amylopectins and their φ,β-limit dextrins (reflecting amylopectin internal structure) from dull1 mutants were also characterized by anion-exchange chromatography after debranching. Deficiency of SSIII led to an increased amount of short chains (DP ≤36 in amylopectin), whereas the content of long chains decreased from 8.4% to between 3.1 and 3.7% in both amylopectin and φ,β-limit dextrins. Moreover, both the external and internal chain lengths decreased, suggesting a difference in their cluster structures. Whereas the molar ratio of A:B-chains was similar in all samples (1.1-1.2), some ratios of chain categories were affected by the absence of SSIII, notably the ratio of "fingerprint" A-chains to "clustered" A-chains. This study highlighted the relationship between SSIII and the internal molecular structure of maize starch.
以具有共同遗传背景（W64A）的 dull1 玉米突变体为材料，研究了缺乏淀粉合酶 III（SSIII）的淀粉的分子结构，并与野生型进行了比较。凝胶渗透色谱分析表明，非蜡质突变体（25.4-30.2%）的直链淀粉含量高于野生型玉米（21.5%），其结构发生了改变。在所有非蜡质样品中都发现了超长支链的支链淀粉组分。通过支链酶解后的阴离子交换色谱，还对 dull1 突变体的支链淀粉和其 φ、β-极限糊精（反映支链淀粉内部结构）的单元链长分布进行了研究。SSIII 的缺乏导致短链（支链淀粉中 DP ≤36）的含量增加，而长链的含量从支链淀粉和 φ、β-极限糊精中的 8.4%分别降低至 3.1-3.7%。此外，内外链长均降低，表明其簇状结构存在差异。虽然所有样品中 A:B-链的摩尔比相似（1.1-1.2），但一些链类别比例受到 SSIII 缺失的影响，特别是“指纹”A-链与“聚集”A-链的比例。本研究强调了 SSIII 与玉米淀粉内部分子结构之间的关系。
