Goldstein Avi, Annor George, Blennow Andreas, Bertoft Eric
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA.
Department of Plant and Environmental Sciences, University of Copenhagen, Denmark.
Int J Biol Macromol. 2017 Sep;102:924-932. doi: 10.1016/j.ijbiomac.2017.04.107. Epub 2017 Apr 28.
The impact of diurnal photosynthetic activity on the fine structure of the amylopectin fraction of starch synthesized by normal barley (NBS) and waxy barley (WBS), the latter completely devoid of amylose biosynthesis, was determined following the cultivation under normal diurnal or constant light growing conditions. The amylopectin fine structures were analysed by characterizing its unit chain length profiles after enzymatic debranching as well as its φ,β-limit dextrins and its clusters and building blocks after their partial and complete hydrolysis with α-amylase from Bacillus amyloliquefaciens, respectively. Regardless of lighting conditions, no structural effects were found when comparing both the amylopectin side-chain distribution and the internal chain fragments of these amylopectins. However, the diurnally grown NBS and WBS both showed larger amylopectin clusters and these had lower branching density and longer average chain lengths than clusters derived from plants grown under constant light conditions. Amylopectin clusters from diurnally grown plants also consisted of a greater number of building blocks, and shorter inter-block chain lengths compared to clusters derived from plants grown under constant light. Our data demonstrate that the diurnal light regime influences the fine structure of the amylopectin component both in amylose and non-amylose starch granules.
在正常昼夜或持续光照生长条件下种植后，测定了昼夜光合活性对正常大麦（NBS）和糯大麦（WBS，后者完全缺乏直链淀粉生物合成）合成的淀粉中支链淀粉部分精细结构的影响。通过分别用解淀粉芽孢杆菌的α-淀粉酶对支链淀粉进行酶解去支化后表征其单位链长分布，以及对其φ,β-极限糊精、簇和结构单元进行部分和完全水解后进行分析，来研究支链淀粉的精细结构。无论光照条件如何，比较这两种支链淀粉的侧链分布和内部链片段时均未发现结构效应。然而，昼夜生长的NBS和WBS都显示出更大的支链淀粉簇，并且这些簇的分支密度低于持续光照条件下生长的植物产生的簇，平均链长更长。与持续光照条件下生长的植物产生的簇相比，昼夜生长的植物的支链淀粉簇还由更多的结构单元组成，且结构单元间的链长更短。我们的数据表明，昼夜光照模式会影响直链淀粉和非直链淀粉颗粒中支链淀粉成分的精细结构。
