Regulation of Plant Enzymes

这是一项为期4年的研究计划，旨在阐明控制光合作用的酶的调节机制。一个关键的机制是胞质果糖-2，6-二磷酸系统，它调节叶片中蔗糖的合成和分解。其目的是：(1)在蛋白质和基因水平上纯化和鉴定新发现的合成和降解2，6-二磷酸果糖的叶酶；(2)确定含有淀粉体的非光合作用(库)组织的这些相同活性是否存在于与叶片相似的酶上。同时，对叶绿体铁氧还蛋白-硫氧还蛋白系统的研究将继续进行，这是一种蛋白质介导的机制，将光与光合作用和相关过程中的酶的调节联系起来。这些研究将(1)推断在分离的叶绿体和叶片中具有催化活性的硫醇在目标酶的光调节中的重要性，以及(2)从作用机制、晶体结构和结构方面表征该系统中剩余的鲜为人知的组成部分--铁氧还蛋白硫氧还蛋白还原酶(FTR)。和EPR/氧化还原特性。这项研究将增加我们对植物如何合成和储存淀粉和蔗糖的理解，这是可食用碳水化合物的主要储存库。

This is a 4 year research program to elucidate the mechanism of regulation of enzymes controlling photosynthesis. One pivotal mechanism is the cytosolic fructose-2,6-bisphosphate system that regulates sucrose synthesis and breakdown in leaves. The objectives are to: (1) purify and characterize at the protein and gene levels newly identified leaf enzymes that synthesize and degrade fructose-2,6-bisphosphate; (2) determine whether these same activities of nonphotosynthetic (sink) tissues containing amyloplasts reside on enzymes similar to those of leaves. In parallel, studies will be continued on the chloroplast ferredoxin-thioredoxin system, a protein-mediated mechanism that links light to the regulation of enzymes functional in photosynthesis and related processes. These studies will (1) deduce the importance of catalytically active thiols in the photoregulation of target enzymes in isolated chloroplasts and leaves, and (2) characterize the remaining poorly understood component of this system--the novel enzyme ferredoxin-thioredoxin reductase (FTR)--with respect to mechanism of action, crystal structure, and EPR/redox properties. This research will increase our understanding of how plants synthesize and store starch and sucrose, the major reservoirs of edible carbohydrate.***