Prinzipien des pflanzlichen Sekundärstoffwechsels

Plant metabolism may be devided in two functional levels: The level of primary metabolism, indispensible for growth and development, and the level of secondary metabolism covering the chemical interactions between organisms, indispensible for survival and maintaining of a species in its ecosystem. Arguments and evidence from various fields of biology are presented in favour of the idea that plant secondary metabolism has most important functions shaped by evolution: historical backgrounds; the difference between plant and animal organisation in respect to defense strategies; the main strategies of plant chemical defense against competitors, predators, and pathogens; complexity of secondary biosynthesis and metabolic integration; variability and richness of structures as essential attributes of secondary metabolism; differences between secondary and primary metabolism are functional not structural.

Vorgetragen auf der Tagung der Deutschen Botanischen Gesellschaft in Wien, September 1984.     

Brassinosteroids fine-tune secondary and primary sulfur metabolism through BZR1-mediated transcriptional regulation

For adaptation to ever-changing environments,plants have evolved elaborate metabolic systems coupled to a regulatory network for optimal growth and defense. Regulation of plant secondary metabolic pathways such as glucosinolates(GSLs) by defense phytohormones in response to different stresses and nutrient deficiency has been intensively investigated, while how growth-promoting hormone balances plant secondary and primary metabolism has been largely unexplored. Here, we found that growth-promotin...     

Action of antibiotics on the growth and metabolic processes of streptomycetes and Nocardia

New experimental data on the effect of novobiocin, ristomycin and nystatin on growth and metabolism of Streptomycetes and Nocardia are presented. The study of the organisms producing other antibiotics showed that they were tens, hundreds and even thousands times more sensitive to the tested biologically active compounds than the organisms producing these compounds. The protein synthesis and antibiotic biosynthesis proved to be most sensitive out of the processes studied. The findings showed that during their evolution the antibiotic-producing organisms have developed definite protective mechanisms which enable them to resist relatively high concentrations of their own metabolites (antibiotics). This ensures them in their struggle for existence.     

链霉菌次级代谢调控相关的双组分系统研究进展

链霉菌具有强大的次级代谢能力, 能够产生众多具有生物活性的次级代谢产物, 如目前广泛应用的抗生素、抗肿瘤药物以及免疫抑制剂等。在链霉菌中, 次级代谢产物的生物合成受到包括途径特异性、多效性以及全局性调控基因在内的多层次严格调控。关键调控基因的缺失或过表达可以显著影响次级代谢产物的生物合成, 提示对于链霉菌次级代谢重要调控基因的功能及其作用机制的研究具有巨大的潜在应用价值。其中, 作为细菌信号传导系统的双组分系统(Two-component system, TCS)一直是大家研究的关注点。越来越多的研究表明TCS在链霉菌次级代谢过程中发挥着全局性的调控功能。本文重点介绍链霉菌模式菌株——天蓝色链霉菌中TCS(包括典型TCS)、孤立的组氨酸蛋白激酶(HK)以及应答调控蛋白(RR)参与次级代谢调控的研究进展。这些TCS的功能鉴定及机制解析为工业链霉菌的定向遗传改造以提高重要次级代谢产物的含量提供了理论依据。     

iTRAQ-based proteomic profiling of a Microbacterium sp. strain during benzo(a)pyrene removal under anaerobic conditions

This study focused on the protein expression of a Microbacterium sp. strain that utilized various concentrations of benzo(a)pyrene (BaP) as the sole source of carbon and energy under anaerobic conditions. A total of 1539 protein species were quantified by isobaric tags for relative and absolute quantitation (iTRAQ) coupled with LC-MS/MS. GO, COG, and pathway enrichment analysis showed that most proteins demonstrated catalytic and binding functions and were mainly involved in metabolic processes, cellular processes, and single-organism processes. Sixty-two proteins were found in their abundances in BaP-stress conditions different from normal conditions. These proteins function in the metabolic pathways; the biosynthesis of secondary metabolites, the biosynthesis of antibiotics, microbial metabolism in diverse environments, carbon metabolism, and the biosynthesis of amino acids were markedly altered. Furthermore, enoyl-CoA hydratase was proposed to be a key protein during BaP removal of the Microbacterium sp. strain. This study provides a powerful platform for the further exploration of BaP removal, and the differentially expressed proteins provide insight into the mechanism of the BaP removal pathway.

     

Microbial transport: Adaptations to natural environments

The cytoplasmic membrane of bacteria is the matrix for metabolic energy transducing processes such as proton motive force generation and solute transport. Passive permeation of protons across the cytoplasmic membrane is a crucial determinant in the proton motive generating capacity of the organisms. Adaptations of the membrane composition are needed to restrict the proton permeation rates especially at higher temperatures. Thermophilic bacteria cannot sufficiently restrict this proton permeation at their growth temperature and have to rely on the much␣lower permeation of Na + to generate a sodium motive force for driving metabolic energy-dependent membrane processes. Specific transport systems mediate passage across the membrane at physiological rates of all compounds needed for growth and metabolism and of all end products of metabolism. Some of transport systems, the secondary transporters, transduce one form of electrochemical energy into another form. These transporters can play crucial roles in the generation of metabolic energy. This is especially so in anaerobes such as Lactic Acid Bacteria which live under energy-limited conditions. Several transport systems are specifically aimed at the generation of metabolic energy during periods of energy-limitation. In their natural environment bacteria are also often exposed to cytotoxic compounds, including antibiotics. Many bacteria can respond to this live-threatening condition by overexpressing powerful drug-extruding multidrug resistance systems.     

Granger causality in integrated GC–MS and LC–MS metabolomics data reveals the interface of primary and secondary metabolism

Metabolomics has emerged as a key technique of modern life sciences in recent years. Two major techniques for metabolomics in the last 10 years are gas chromatography coupled to mass spectrometry (GC–MS) and liquid chromatography coupled to mass spectrometry (LC–MS). Each platform has a specific performance detecting subsets of metabolites. GC–MS in combination with derivatisation has a preference for small polar metabolites covering primary metabolism. In contrast, reversed phase LC–MS covers large hydrophobic metabolites predominant in secondary metabolism. Here, we present an integrative metabolomics platform providing a mean to reveal the interaction of primary and secondary metabolism in plants and other organisms. The strategy combines GC–MS and LC–MS analysis of the same sample, a novel alignment tool MetMAX and a statistical toolbox COVAIN for data integration and linkage of Granger Causality with metabolic modelling. For metabolic modelling we have implemented the combined GC–LC–MS metabolomics data covariance matrix and a stoichiometric matrix of the underlying biochemical reaction network. The changes in biochemical regulation are expressed as differential Jacobian matrices. Applying the Granger causality, a subset of secondary metabolites was detected with significant correlations to primary metabolites such as sugars and amino acids. These metabolic subsets were compiled into a stoichiometric matrix N. Using N the inverse calculation of a differential Jacobian J from metabolomics data was possible. Key points of regulation at the interface of primary and secondary metabolism were identified.     

柞蚕蛹培养蛹虫草不同时间后的代谢组分析

为了解柞蚕蛹培养蛹虫草（简称柞蚕蛹虫草）不同时间后的代谢物变化规律,利用广泛靶向代谢组学技术,比较不同培养时期的柞蚕蛹虫草代谢产物成分,找出差异代谢物并进行代谢通路分析。在柞蚕蛹虫草的5个生长时期共检测到10类421种化合物,主要包括：氨基酸及其衍生物、核苷酸及其衍生物、萜类、酚酸、有机酸、糖及醇类、甾体、脂类、生物碱、醌类等多种化合物。主成分分析（PCA）结果显示,不同生长时期柞蚕蛹虫草的代谢组表现出不同的代谢特征,5个生长时期样本在得分图中可分为3个不同区域,对照（S1）与子座形成初期（S3）归为一区,菌核期（S2）独自归为一区,子座形成期（S4）和子囊壳形成期（S5）归为一区。S2-S5筛选到的特有差异代谢物有36种,包括虫草素、甘露醇等主要活性物质,其中香豆酰腐胺、五羟色胺、γ-生育三烯酚等物质首次被检测到。对不同生长阶段变化排在前20的差异显著代谢成分进行分析,结果表明上下调幅度较大的物质多为有机酸、酚酸、生物碱、核苷酸及其衍生物等次生代谢产物。5个生长时期筛选出的所有差异代谢物共富集在154条代谢通路上,差异代谢物数量富集最多的前5条通路,分别为代谢途径、次生代谢物的生物合成、ABC转运蛋白、嘌呤代谢和氨酰生物合成。整个生长周期中,具有显著影响的通路是嘌呤代谢与丙氨酸、天门冬氨酸和谷氨酸代谢途径。本研究结果可为柞蚕蛹虫草的深入研究与应用提供参考。     

植物毛状根的培养及其化学进展：2.植物毛状根的次生代谢

本文介绍了毛状根的次生代谢调控、次生代谢物质的生产、生物转化、生物合成以及工业化应用。     

Critical analysis of protein signaling networks involved in the regulation of plant secondary metabolism: focus on anthocyanins

Anthocyanin biosynthesis in Arabidopsis is a convenient and relatively simple model for investigating the basic principles of secondary metabolism regulation. In recent years, many publications have described links between anthocyanin biosynthesis and general defense reactions in plants as well as photomorphogenesis and hormonal signaling. These relationships are complex, and they cannot be understood intuitively. Upon observing the lacuna in the Arabidopsis interactome (an interaction map of the factors involved in the regulation of Arabidopsis secondary metabolism is not available), we attempted to connect various cellular processes that affect anthocyanin biosynthesis. In this review, we revealed the main signaling protein modules that regulate anthocyanin biosynthesis. To our knowledge, this is the first reconstruction of a network of proteins involved in plant secondary metabolism.     

Combinatorial biosynthesis of medicinal plant secondary metabolites

Combinatorial biosynthesis is a new tool in the generation of novel natural products and for the production of rare and expensive natural products. The basic concept is combining metabolic pathways in different organisms on a genetic level. As a consequence heterologous organisms provide precursors from their own primary and secondary metabolism that are metabolised to the desired secondary product due to the expression of foreign genes. In this review we discuss the possibilities and limitations of combining genes from different organisms and the expression of heterologous genes. Major focuses are fundamentals of the genetic work, used expression systems and latest progress in this field. Combinatorial biosynthesis is discussed for important classes of natural products, including alkaloids (vinblastine, vincristine), terpenoids (artemisinin, paclitaxel) and flavonoids. The role and importance of today's used host organisms is critically described, and the latest approaches discussed to give an outlook for future trends and possibilities.     

辅因子在微生物细胞工厂中的代谢调控与应用*

生物体中大部分酶催化反应都需要辅因子参与,辅因子平衡对维持正常的细胞代谢至关重要,而辅因子失衡则会导致细胞生长和生产的紊乱。在微生物细胞工厂的构建中,通过调节辅因子代谢平衡来提高产物合成途径的效率,从而调控细胞生长与产物生产,使代谢流能够最大限度地流向目标产物,已经成为代谢调控的重要手段。目前常见的用于代谢调控的辅因子有NAD(P)H/NAD(P)⁺、辅酶、ATP/ADP等。围绕这几种辅因子的代谢途径及功能分类进行了综述,并总结了微生物中不同产物利用辅因子平衡策略进行合成调控的研究,以期为各类化合物的高效生物合成提供参考。     

Catharanthus biosynthetic enzymes: the road ahead

Alkaloids are one of the most diverse groups of secondary metabolites found in living organisms. The most economically important alkaloids are the bisindole vinblastine, and vincristine. Unraveling the complexity of the genetic, catalytic and transport processes of monoterpene indole alkaloids biosynthesis is one of the most stimulating intellectual challenges in the plant secondary metabolism field. More than 50 metabolic steps are required to synthesize the most important alkaloids in Catharanthus roseus. Until now about only 20 of the 50 enzymes required for their biosynthesis have been determined and characterized. Hence, there are still a number of important enzymes that need to be characterized, beginning with the isolation and cloning of genes. It is also of fundamental importance to elucidate the regulatory aspects of their biosynthesis, both at the cellular and the molecular level, in order to address the question of their function in the plants that are producing them. In this review, we present an analysis of the state of the art related to the biosynthesis of the monoterpene indole alkaloids.     

On the evolution of functional secondary metabolites (natural products)

It is argued that organisms have evolved the ability to biosynthesize secondary metabolites (natural products) because of the selectional advantages they obtain as a result of the functions of the compounds. The clustering together of antibiotic biosynthesis, regulation, and resistance genes implies that these genes have been selected as a group and that the antibiotics function in antagonistic capacities in nature. Pleiotropic switching, the simultaneous expression of sporulation and antibiotic biosynthesis genes, is interpreted in terms of the defence roles of antibiotics. We suggest a general mechanism for the evolution of secondary metabolite biosynthesis pathways, and argue against the hypothesis that modern antibiotics had prebiotic effector functions, on the basis that it does not account for modern biosynthetic pathways.