Lignins, (Oligo)lignans, and

木质素、（寡聚）木脂素和

• 批准号: 9976684
• 负责人: Norman Lewis
• 金额: $ 27万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9976684&HistoricalAwards=false
• 关键词: Lignins; Oligo; lignans

Lewis This particular project will establish as the first objective whether an entire class of dirigent proteins exists in Eucommia, Linum, Schizandra and Larrea species, and which individually differ in the distinctive 8-8' coupling modes stipulated. It is anticipated that each selected plant species harbors a distinct dirigent protein which differs in either preferred substrate utilized and/or stereoselectivity engendered during radical-radical coupling. Using either cDNA library screening and/or RT-PCR approaches, the dirigent protein homologues from each species will be obtained, with specific coupling modes encoded determined through heterologous expression of functionally competent recombinant dirigent proteins. Additionally, this phase of the study will include identifying the tissues and developmental stages involved in dirigent protein gene expression/protein localization in these particular species, at tissue and (sub)cellular levels. In the second objective of this study, we will seek to demonstrate that lignification in the plant cell wall is stipulated through the participation of arrays of dirigent protein sites (or an equivalent thereof) which control both linkage type and monomer(s) involved. Particular attention will be given to demonstrating formation of the so-called 8-O-4' linkage in lignins obtained in vitro, since this linkage predominates in lignins in vivo. The lignin biopolymers and (oligomeric) lignans account for nearly 30% of organic carbon circulating in the biosphere, being major constituents of vascular plants. The lignins are structural cell wall constituents without which plants would be unable to either stand vertically and/or form their woody tissues; the (oligomeric) lignans, while derived from the same precursors as lignins, are employed in plant defense roles (e.g. as antioxidants, bactericides, antiviral and antifeedant compounds, etc.). The current project builds on our recent discovery of dirigent proteins which, in turn, gives incisive insight into at least one of the principal mechanisms whereby living organisms (plants) can control the outcome of radical-radical coupling. Until this discovery, such conversions had been considered as solely in the realm of non-specific oxidative conversions, such as those catalyzed by O2/laccases and peroxidases/H2O2.

刘易斯这个特别的项目将建立作为第一个目标的是，杜仲、亚麻、五味子和五味子中是否存在一整类调控蛋白，以及它们各自在所规定的独特的8-8‘偶联模式上的不同。预计每个选定的植物物种都含有一种不同的营养蛋白质，这种蛋白质在自由基-自由基耦合过程中所利用的首选底物和/或产生的立体选择性不同。利用文库筛选和/或RT-PCR方法，将获得每个物种的介导性蛋白同源物，并通过异源表达具有功能的重组介导性蛋白来确定特定的偶联模式。此外，这一阶段的研究将包括在组织和(亚)细胞水平上确定在这些特定物种中参与差异蛋白基因表达/蛋白定位的组织和发育阶段。在这项研究的第二个目标中，我们将试图证明，植物细胞壁中的木质化是通过参与控制连锁类型和所涉及的单体(S)的一系列渗透蛋白位点(或其等价物)来规定的。将特别注意证明在体外获得的木质素中所谓的8-O-4‘键的形成，因为这一键在体内木质素中占主导地位。木质素生物聚合物和低聚木脂素占生物圈中循环的有机碳的近30%，是维管束植物的主要成分。木质素是一种结构性的细胞壁成分，如果没有木质素，植物将不能垂直站立和/或形成木质组织；(低聚)木脂素虽然来自与木质素相同的前体，但被用于植物防御作用(例如，作为抗氧化剂、杀菌剂、抗病毒和拒食化合物等)。目前的项目建立在我们最近发现的引导性蛋白质的基础上，这反过来又为生物有机体(植物)控制自由基-自由基耦合的结果提供了至少一个主要机制的深刻见解。在这一发现之前，这种转化一直被认为仅属于非特异性氧化转化的领域，例如由O2/漆酶和过氧化物酶/过氧化氢催化的氧化转化。