Regulation of Plant Enzymes

这是一个为期4年的研究项目，旨在阐明酶对光合作用的调控机制。其中一个关键机制是调节叶片中蔗糖合成和分解的胞质果糖-2,6-二磷酸系统。目的是：(1)在蛋白质和基因水平上纯化和表征新鉴定的合成和降解果糖-2,6-二磷酸的叶片酶；(2)确定含有淀粉体的非光合（汇）组织的这些相同活动是否存在于类似于叶片的酶上。与此同时，叶绿体铁氧化还蛋白-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功能酶的调节联系起来。这些研究将(1)推断出催化活性硫醇在分离的叶绿体和叶片中靶酶的光调节中的重要性，(2)表征该系统中剩余的知之甚少的组成部分-新型酶铁氧化还蛋白-硫氧还蛋白还原酶(FTR)-关于作用机制，晶体结构，EPR/氧化还原性能。这项研究将增加我们对植物如何合成和储存淀粉和蔗糖这两种可食用碳水化合物的主要储存库的理解

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.***