Functional Expression of a Starch Biosynthetic System in Yeast

植物淀粉是人类饮食中最重要的热量来源，也是广泛应用于工业领域的可再生资源。组成淀粉的葡萄糖聚合物的化学结构相对简单，然而，在建筑意义上，这些分子表现出几个层次的结构复杂性。负责产生这种结构有序产物的生物合成机制在很大程度上是未知的。这些机制是这项研究项目的主题，这是合理的，因为有可能改变植物中的淀粉生产用于实际应用，也可以收集关于生物合成活性和产品结构结构之间关系的基本生物学信息。近年来，人们已经分离出了产生淀粉的酶，并克隆了它们的编码基因。一般的观察是，对于这个过程中的每一种酶，即淀粉合成酶、淀粉分支酶和淀粉去分支酶，都存在多种形式。为了简化系统，这项研究项目将使用基因工程技术，将淀粉生物合成酶从玉米粒的自然环境中逐一转移到酵母细胞中。这项技术允许在一个酵母菌株中结合几个玉米基因。然后将分析由这些酶形成的葡萄糖聚合物的结构。从这些数据中，我们可能能够辨别出由每种酶赋予的淀粉的特定结构特征，无论是单独的还是与其他酶的特定组合。这些知识有望对未来将淀粉作为可再生资源开发的研究有用。

Plant starches are the most important calorie source in the human diet and also are renewable resources for a wide variety of industrial applications. The chemical structure of the glucose polymers that make up starch is relatively simple, however, in an architectural sense, these molecules exhibit several hierarchical levels of structural complexity. The biosynthetic mechanisms responsible for producing such a structurally ordered product are largely unknown. These mechanisms are the subject of this research project, which is justified owing to the potential to modify starch production in plants for practical applications, and also for gathering fundamental biological information about the relationship between biosynthetic activity and architectural structure of the product. The enzymes that produce starch have been isolated in recent years, and the genes that code for them have been cloned. A general observation is that for each enzyme in the process, that is, the starch synthases, the starch branching enzymes, and the starch debranching enzymes, multiple forms exist. To try to simplify the system, this research project will use genetic engineering techniques to move the starch biosynthetic enzymes one at a time from their native environment in maize kernels into yeast cells. The technology allows combination of several maize genes in one yeast strain. The structure of the glucose polymers that are formed by these enzymes will then be analyzed. From these data we may be able to discern the specific structural characteristics of starch that are imparted by each enzyme, either alone or in specific combinations with other This knowledge is expected to be useful for future research directed at exploiting starch as a renewable resource.