Hanashiro Isao
1 Department of Food Science and Biotechnology, Kagoshima University.
2 Course of Biological Science and Technology, The United Graduate School of Agricultural Sciences, Kagoshima University.
J Appl Glycosci (1999). 2024 Nov 20;71(4):111-116. doi: 10.5458/jag.jag.JAG-2024_0009. eCollection 2024.
The branched structure of amylose was probed using concanavalin A (ConA) lectin, which forms precipitable aggregates with highly branched glucans, such as glycogen and amylopectin. Rice (japonica cultivar) amylose was fractionated from de-fatted, gelatinized starch by precipitation with 1-butanol (BuOH) and purified by ultracentrifugation and repeated crystallization. The purified amylose still has short side chains, whose chain-length (CL) distribution resembles that of amylopectin. More than 96 wt% of the amylose was not precipitated with ConA and remained in the resultant supernatant. The amylose recovered from the supernatant exhibited essentially the same size distributions of molecules and the CL distributions of main and side chains as those of amylose without ConA precipitation. The molar % of branched molecules was slightly decreased by ConA precipitation (-ConA, 11.6; +ConA, 8.1). These results suggest that the side chains detected in BuOH-precipitable amylose preparation are essentially attributable to amylose itself. Also, the non-precipitable nature of the branched molecules of amylose by ConA supports our previous proposal that the organization of the short side chains on amylose molecules is quite different from that found in amylopectin, in which the short side chains are arranged in a cluster fashion, and the branched glucan interacts with ConA to form precipitable aggregates. A tiny amount of ConA-precipitable glucan was detected, but its CL distribution was inconsistent with the size distribution of the branched molecules. Even if the precipitable glucans were fragments of amylopectin, their contribution to the branches detected in amylose should be minor.
使用伴刀豆球蛋白A（ConA）凝集素探测直链淀粉的分支结构，该凝集素可与高度分支的葡聚糖（如糖原和支链淀粉）形成可沉淀的聚集体。通过用正丁醇（BuOH）沉淀从脱脂、糊化的淀粉中分离出水稻（粳稻品种）直链淀粉，并通过超速离心和反复结晶进行纯化。纯化后的直链淀粉仍具有短侧链，其链长（CL）分布类似于支链淀粉。超过96 wt%的直链淀粉未与ConA沉淀，而是留在了所得的上清液中。从上清液中回收的直链淀粉在分子大小分布以及主链和侧链的CL分布方面，与未经ConA沉淀的直链淀粉基本相同。ConA沉淀使分支分子的摩尔百分比略有下降（-ConA为11.6；+ConA为8.1）。这些结果表明，在BuOH可沉淀的直链淀粉制剂中检测到的侧链基本上归因于直链淀粉本身。此外，直链淀粉的分支分子不被ConA沉淀的性质支持了我们之前的提议，即直链淀粉分子上短侧链的排列方式与支链淀粉中的截然不同，在支链淀粉中短侧链以簇状排列，且分支葡聚糖与ConA相互作用形成可沉淀的聚集体。检测到少量可被ConA沉淀的葡聚糖，但其CL分布与分支分子的大小分布不一致。即使可沉淀的葡聚糖是支链淀粉的片段，它们对直链淀粉中检测到的分支的贡献也应该很小。
