Regulation of Assimilatory Nitrate Reductase

硝酸盐同化途径是无机氮转化为生物上有用的有机形式的主要途径。调控这一途径的第一步，由硝酸盐还原酶（NR）催化，对于防止中间体（亚硝酸盐和氨）的毒性积累，确保硝酸盐的有效利用，以及允许快速适应环境条件的变化至关重要。以往的研究结果表明，NR受到多种效应物和环境因素在多个不同水平上的调控，反映了该酶的关键作用和通路调控的生物学重要性。我们的研究将集中在分子（酶）水平上阐明NR调控的重要分子决定因素和机制，并建立各种调控模式之间的相互关系。具体目标将包括：a)识别参与NR转换、催化、结合或调节的功能基团，以及这些基团在酶的功能域或一级序列位点上的定位；b)确定可能的活性调节剂，如蛋白激酶/磷酸酶、金属结合效应剂（如一氧化氮或氰化物）或其他效应剂对NR转化和催化效率的影响。我们研究的最终目标是从本研究和其他研究中获得信息，以开发提高NR的催化效率和调节其作用的程序，以提高农业生产力。硝酸盐是生物体内有机氮的主要来源。硝酸盐被转化为生物上有用的有机形式的过程，称为硝酸盐同化，发生在各种各样的生物中，包括细菌、酵母、真菌和高等植物，它们反过来为包括人类在内的其他生命形式提供营养氮的需求。本研究的目标之一是制定提高催化效率和调节硝酸盐同化途径中关键酶硝酸还原酶（NR）活性的策略。我们目前的研究重点是确定NR分子的官能团和其他因素，这将有助于我们更多地了解蛋白质。然后，我们可以利用这些信息来设计农业上有趣的植物，使其具有更有效的氮代谢和更高的生产能力。氮代谢改善的植物将减少作物对化肥的需求。＊＊＊

Solomonson 9317557 The nitrate assimilatory pathway is the major route by which inorganic nitrogen is converted to a biologically useful organic form. Regulation of the first step in this pathway, catalyzed by nitrate reductase (NR), is important to prevent toxic accumulation of intermediates (nitrite and ammonia), to assure efficient utilization of nitrate, and to permit rapid adaptation to changes in environmental conditions. Results of previous studies have indicated that NR is regulated at several different levels by multiple effectors and environmental factors reflecting the key role of this enzyme and the biological importance of pathway regulation. Our research will focus on elucidating molecular determinants and mechanisms which are important for the regulation of NR at the molecular (enzyme) level and establishing interrelationships between various modes of regulation. Specific aims will include: a) identification of functional groups involved in NR turnover, catalysis, binding or regulation, and the localization of these groups with respect to functional domain or primary sequence site on the enzyme; and b) determination of effects of possible activity modulators such as protein kinases/phosphatases, metal binding effectors (e.g., nitric oxide or cyanide), or other effectors on NR turnover and catalytic efficiency. The ultimate goal of our research is to obtain information from this and other studies to develop procedures for increasing the catalytic efficiency of NR and for regulating its action in an effort to increase agricultural productivity. %%% Nitrate is the major source of organic nitrogen in biological organisms. The process by which nitrate is converted to a biologically useful, organic form, termed nitrate assimilation, occurs in a wide variety of organisms including bacteria, yeast, fungi and higher plants, which in turn supply the nutritional nitrogen requirements for other forms of life, including human. One of the goals of this r esearch is to develop strategies for increasing the catalytic efficiency and for regulating the activity of the key enzyme, nitrate reductase (NR), in the nitrate assimilation pathway. The focus of our current research program is to identify the functional groups of the NR molecule and other factors that will help us learn more about the protein. We may then use this information to engineer agriculturally interesting plants with more efficient nitrogen metabolism and increased production capacity. Plants with improved nitrogen metabolism will result in decreased need to supply chemical fertilizers to our crops. ***