The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia.
The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia; Joint International Research Laboratory of Agriculture and Agri-Product Safety, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu Province, China.
Carbohydr Polym. 2019 Nov 15;224:115185. doi: 10.1016/j.carbpol.2019.115185. Epub 2019 Aug 10.
Starch branching enzymes (SBEs) play a major role in determining starch molecular structure in cereal endosperm. This study investigates how SBEIIs contribute to the chain-length distributions (CLDs) of both amylopectin and amylose, obtained by enzymatic debranching of native starch. Wheat starches with low (37%) to high (93%) amylose content were obtained through altering SBEII in planta. Multiple components were detected in both amylose and amylopectin CLDs. Model fitting of these CLDs reveals a quantitative association between the enzyme activities in amylopectin and amylose. SBEIIa modifies shorter branches (degree of polymerization DP ≲ 12) in amylopectin and longer amylose chains with a CLD peak at ˜3000 DP. SBEIIb acts on longer branches (DP≲ 32) in amylopectin, while its effect on amylose fine structure is not significant. Using both the amylose and amylopectin models to analyze the CLD reveals connections between amylose and amylopectin in wheat starch biosynthesis.
淀粉分支酶（SBEs）在决定谷物胚乳中淀粉分子结构方面起着重要作用。本研究探讨了 SBEII 如何影响通过天然淀粉的去分支酶解获得的支链淀粉和直链淀粉的链长分布（CLD）。通过在植物体内改变 SBEII，获得了直链淀粉含量低（37%）至高（93%）的小麦淀粉。在支链淀粉和直链淀粉的 CLD 中均检测到多个成分。对这些 CLD 的模型拟合表明，支链淀粉和直链淀粉中酶活性之间存在定量关联。SBEIIa 修饰支链淀粉中较短的分支（聚合度 DP ≲ 12）和较长的直链淀粉链，其 CLD 峰值在 ≈3000 DP。SBEIIb 作用于支链淀粉中的较长分支（DP≲ 32），但其对直链淀粉精细结构的影响并不显著。使用支链淀粉和直链淀粉模型来分析 CLD 揭示了小麦淀粉生物合成中直链淀粉和支链淀粉之间的联系。
