The elongation of amylose and amylopectin chains in isolated starch granules
The elongation of amylose and amylopectin chains in isolated starch granules
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DOI：
10.1046/j.1365-313x.1996.10061135.x
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发表时间：
1996-12-01
期刊：
影响因子：
7.2
通讯作者：
Smith, AM
中科院分区：
文献类型：
--
作者：
Denyer, K;Clarke, B;Smith, AM
本工作的目的是研究淀粉颗粒中直链淀粉合成所需的条件。虽然淀粉合成酶的主要颗粒结合异型- GBSSI -在体内催化直链淀粉的合成，但当提供给从豌豆（Pisum sativum L.）胚胎和马铃薯（Solanum tuberosum L.）块茎分离的淀粉颗粒时，来自ADP[C-14]葡萄糖的C-14主要结合到支链的特定亚群中。用这些器官的可溶性提取物对颗粒进行孵育，发现提取物中含有增加C-14与直链淀粉结合的化合物。这些化合物经α -葡萄糖苷酶处理后失去活性，表明它们是麦芽糖寡糖。与这一观点一致的是，将纯麦芽寡糖提供给分离的颗粒导致C-14的结合模式发生了巨大的变化，从支链淀粉链到直链淀粉分子。通过比较野生型豌豆和缺乏GBSSI的蓝豆突变体豌豆颗粒中麦芽麦寡糖的掺入模式，发现麦芽麦寡糖对GBSSI的影响是特异性的。讨论了这些结果对了解贮藏器官中直链淀粉和支链淀粉合成的意义。
The aim of this work was to investigate the conditions required for amylose synthesis in starch granules. Although the major granule-bound isoform of starch synthase - GBSSI - catalyses the synthesis of amylose in vivo, C-14 from ADP[C-14]glucose was incorporated primarily into a specific subset of amylopectin chains when supplied to starch granules isolated from pea (Pisum sativum L.) embryos and potato (Solanum tuberosum L.) tubers. Incubation of granules with soluble extracts of these organs revealed that the extracts contained compounds that increased the incorporation of C-14 into amylose. These compounds were rendered inactive by treatment of the extracts with alpha-glucosidase, suggesting that they were malto-oligosaccharides. Consistent with this idea, provision of pure malto-oligosaccharides to isolated granules resulted in a dramatic shift in the pattern of incorporation of C-14, from amylopectin chains to amylose molecules. Comparison of the pattern of incorporation in granules from wild-type peas and lam mutant peas which lack GBSSI showed that this effect of malto oligosaccharides was specifically on GBSSI. The significance of these results for understanding of the synthesis of amylose and amylopectin in storage organs is discussed.