A parameterized model of amylopectin synthesis provides key insights into the synthesis of granular starch.
A parameterized model of amylopectin synthesis provides key insights into the synthesis of granular starch.
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DOI：
10.1371/journal.pone.0065768
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Gilbert RG
中科院分区：
文献类型：
--
作者：
Wu AC;Morell MK;Gilbert RG
基因研究已经确定了一组与淀粉合成有关的核心基因，但淀粉生物合成的复杂性阻碍了人们对所编码的酶的精确功能作用的研究。支链淀粉在谷类胚乳中的链长分布(CLD)是由淀粉合成酶、分支酶和去分支酶及其各自的异构体三种酶协同作用产生的。该模型以及对实验的拟合，提供了四个关键见解。(1)为了产生结晶淀粉，对酶活性的特定比例进行了限定的限制。(2)对以前仅从遗传研究中得出的结论的独立确认，该结论是结晶支链淀粉合成中对脱支酶的绝对需求。(3)该模型为理解连续的晶片阵列是如何形成的提供了力学基础，该模型基于两种独立的长支链支链的鉴定，一种类型保留在无定形晶片中，而另一种传播到相邻的晶片中，并且是形成相邻晶片所必需的。(4)该模型提供了一种方法，可以从支链淀粉CLD中推导出定义核心酶活性的少量关键参数，为集中研究产生特定结构的淀粉的酶需求提供了基础。该建模方法提供了一种新的工具来加速了解颗粒淀粉的生物合成，也为利用一系列基于稳健机制框架的可测试预测来操纵淀粉的结构和功能提供了基础。
A core set of genes involved in starch synthesis has been defined by genetic studies, but the complexity of starch biosynthesis has frustrated attempts to elucidate the precise functional roles of the enzymes encoded. The chain-length distribution (CLD) of amylopectin in cereal endosperm is modeled here on the basis that the CLD is produced by concerted actions of three enzyme types: starch synthases, branching and debranching enzymes, including their respective isoforms. The model, together with fitting to experiment, provides four key insights. (1) To generate crystalline starch, defined restrictions on particular ratios of enzymatic activities apply. (2) An independent confirmation of the conclusion, previously reached solely from genetic studies, of the absolute requirement for debranching enzyme in crystalline amylopectin synthesis. (3) The model provides a mechanistic basis for understanding how successive arrays of crystalline lamellae are formed, based on the identification of two independent types of long amylopectin chains, one type remaining in the amorphous lamella, while the other propagates into, and is integral to the formation of, an adjacent crystalline lamella. (4) The model provides a means by which a small number of key parameters defining the core enzymatic activities can be derived from the amylopectin CLD, providing the basis for focusing studies on the enzymatic requirements for generating starches of a particular structure. The modeling approach provides both a new tool to accelerate efforts to understand granular starch biosynthesis and a basis for focusing efforts to manipulate starch structure and functionality using a series of testable predictions based on a robust mechanistic framework.
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影响因子：
3.1
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