通过下调生物合成酶来改变甘薯淀粉薄片中的纳米级链组装。

Changes in Nanoscale Chain Assembly in Sweet Potato Starch Lamellae by Downregulation of Biosynthesis Enzymes.

机构信息

Group for Cereals and Oils Processing, Key Laboratory of Environment Correlative Dietology (Ministry of Education), College of Food Science and Technology , Huazhong Agricultural University , Wuhan 430070 , China.

National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences , Chinese Academy of Sciences , Shanghai 200032 , China.

出版信息

J Agric Food Chem. 2019 Jun 5;67(22):6302-6312. doi: 10.1021/acs.jafc.8b06523. Epub 2019 Apr 10.

DOI:10.1021/acs.jafc.8b06523

PMID:30925057

Abstract

Granule-bound starch synthase I (GBSSI) and starch-branching enzymes I and II (SBEI and SBEII) are crucial enzymes that biosynthesize starches with varied apparent amylose contents and amylopectin branching structure. With a sweet potato ( Ipomoea batatas [L.] Lam. cv. Xushu22), this work shows that downregulating GBSSI (for waxy starch) or SBE (for high-amylose starch) activity allowed the formation of new semicrystalline lamellae (named Type II) in sweet potato starch in addition to the widely reported Type I lamellae. Small-angle X-ray scattering (SAXS) results show that, compared with Type I lamellae, Type II lamellae displayed increased average thickness and thickness-distribution width, with thickened amorphous and crystalline components. The size-exclusion-chromatography (SEC) data revealed mainly two enzyme sets, (i) and (ii), synthesizing amylopectin chains. Reducing the GBSSI or SBE activity increased the amounts of amylopectin long chains (degree of polymerization (DP) ≥ 33). Combined SAXS and SEC analyses indicate that parts of these long chains from enzyme set (i) could be confined to Type II lamellae, followed by DP ≤ 32 short chains in Type I lamellae and the rest of the long chains from enzyme sets (i) and (ii) spanning more than a single lamella.

摘要

颗粒结合型淀粉合成酶 I（GBSSI）和淀粉分支酶 I 和 II（SBEI 和 SBEII）是生物合成具有不同表观直链淀粉含量和支链淀粉分支结构的淀粉的关键酶。以甘薯（Ipomoea batatas [L.] Lam. cv. Xushu22）为例，本工作表明，下调 GBSSI（用于生产蜡质淀粉）或 SBE（用于生产高直链淀粉淀粉）的活性可使除了广泛报道的 I 型片层外，还可在甘薯淀粉中形成新的半结晶片层（命名为 II 型）。小角 X 射线散射（SAXS）结果表明，与 I 型片层相比，II 型片层显示出增加的平均厚度和厚度分布宽度，具有增厚的无定形和结晶成分。尺寸排阻色谱（SEC）数据显示主要有两组酶（i）和（ii）合成支链淀粉链。降低 GBSSI 或 SBE 活性会增加支链淀粉长链（聚合度（DP）≥33）的数量。结合 SAXS 和 SEC 分析表明，来自酶组（i）的这些长链的一部分可以被限制在 II 型片层中，然后是 DP≤32 的短链在 I 型片层中，其余来自酶组（i）和（ii）的长链跨越超过一个片层。