The University of Queensland, Center for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia.
The University of Queensland, School of Chemistry and Molecular Biosciences, Brisbane, QLD 4072, Australia.
Food Chem. 2020 Nov 15;330:127328. doi: 10.1016/j.foodchem.2020.127328. Epub 2020 Jun 12.
Granular protein is an important structural feature in determining starch digestibility. High-amylose wheat starch (HAWS) with >80% amylose content contains more granular protein than wild-type starch. As analyzed by mass spectrometry-based proteomics, granular-bound starch synthase (GBSS) is the major granular protein in isolated starch materials. GBSS content increases with amylose content (Spearman's correlation, p < 0.05), whereas the abundance relative to other proteins is similar among starches. Multiple amylase inhibitors were also identified. From Michaelis-Menten analysis, HAWS has a similar K (Michaelis constant) as wild type, suggesting initial enzymatic binding is similar. After the pre-digestion of proteins, wild type had a greater change in starch digestibility than HAWS, probably due to the latter having 'thicker' granular-protein layers and higher enzymatic resistance of substrate per se. Overall, the study suggests that the greater granular protein content in HAWS is a factor that contributes to slower amylolysis compared to wild type.
颗粒蛋白是决定淀粉消化率的重要结构特征。直链淀粉含量超过 80%的高直链小麦淀粉（HAWS）比野生型淀粉含有更多的颗粒蛋白。通过基于质谱的蛋白质组学分析，颗粒结合型淀粉合成酶（GBSS）是分离淀粉材料中的主要颗粒蛋白。GBSS 含量随直链淀粉含量增加而增加（Spearman 相关性，p < 0.05），而与其他蛋白质的相对丰度在淀粉之间相似。还鉴定了多种淀粉酶抑制剂。从米氏动力学分析，HAWS 的 K（米氏常数）与野生型相似，表明初始酶结合相似。在蛋白质预消化后，野生型的淀粉消化率变化大于 HAWS，可能是由于后者的颗粒蛋白层更厚，以及底物本身的酶抗性更高。总的来说，该研究表明，HAWS 中较高的颗粒蛋白含量是导致其与野生型相比淀粉水解速度较慢的一个因素。
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