多组分反应在吡咯衍生物合成中的应用进展

多组分反应(Multicomponent Coupling Reactions,MCRs)是将三种或三种以上的相对简单的原料加入"一锅煮"反应中,不经过中间体分离而直接得到结构复杂的分子的方法。具有操作简单、原料易得、环境友好等优点。多组分反应发展至今,已经在包括药物合成的多个领域中起到了重要作用。吡咯衍生物作为一类在自然界中广泛分布、有着重要生物医药价值和材料科学价值的重要化合物,其合成方法一直是有机合成研究中的热点之一。近年来用于合成吡咯衍生物的多组分反应也不断地被报道。多组分反应能够很好地解决传统吡咯合成路线中取代基引入的问题并能提高反应收率,为吡咯衍生物的合成与研究带来便利。本文从合成方法上概述了近年来多组分反应在吡咯合成中的应用,为合成已有吡咯衍生物和探寻全新结构的吡咯衍生物提供合成方法上的新思路。     

小麦胆色素原脱氨酶的纯化及部分性质研究

生物中四吡咯化合物合成的共同途径是由δ－氨基酮戊酸（δ－ａｍｉｎｏｌｅｖｕｌｉｎｉｃａｃｉｄ,ＡＬＡ）在δ－氨基酮戊酸脱水酶（δ－ａｍｉｎｏｌｅｖｕｌｉｎａｔｅｄｅｈｙｄｒａｔａｓｅ,ＡＬＡＤ）作用下合成胆色素原（ｐｏｒｐｈｏ－ｂｉｌｉｎｏｇｅｎ,Ｐ...     

二硫吡咯酮类抗生素的生物合成与代谢工程应用北大核心CSCD

二硫吡咯酮类抗生素是一类具有独特的吡咯酮二硫杂环戊二烯(4H-[1,2]二硫[4,3-b]吡咯-5-酮)骨架的化合物的总称。基于N-7位酰基侧链的不同以及N-4位是否含有甲基,可分为N-methyl-Nacylpyrrothine、N-acylpyrrothine和thiomarinols等类别。迄今为止,已有27种该类化合物被报道,重要代表包括全霉素(holomycin)、硫藤黄菌素(thiolutin)、金霉素(aureothricin)以及最近发现的thiomarinols。就生物活性而言,二硫吡咯酮类抗生素具有广谱的抗细菌活性,对多种微生物,包括革兰氏阴性菌、革兰氏阳性菌以及寄生虫都有较好的杀灭活性。甚至一些二硫吡咯酮衍生物表现出较强的抗肿瘤活性。近几年来,多个二硫吡咯酮类抗生素的生物合成基因簇相继被报道,其生物合成机理也逐步被阐明。本文将针对目前国内外二硫吡咯酮类抗生素的生物合成研究进展,以及在组合生物合成与代谢工程领域所取得的成果进行综述,旨在为通过合成生物学的方法创造结构新颖、高效低毒的"非天然"二硫吡咯酮类化合物提供理论借鉴。     

新型N-取代吡咯类化合物的体外抗肿瘤活性研究

目的:研究37个新型N-取代吡咯类化合物的体外抗肿瘤活性,并探讨这些化合物的结构-活性关系。方法:运用MTT法来测试37个化合物对5种肿瘤细胞和1种正常细胞的体外细胞增殖抑制活性。结果:化合物3f活性最高,其对MGC80-3的IC50值为61.29μM。同时成功地总结了新型N-取代吡咯化合物的构效关系:(1)对于吡咯母核的3位,取代苯环上对位氯取代和对位叔丁基取代化合物的抗肿瘤活性差不多,并且没有明显的规律性。(2)对于吡咯母核的4位,取代基团的电子云密度对抗肿瘤活性的影响也没有明显的规律。(3)对于吡咯母核的1位,当3位为对叔丁基苯基取代时,其整体活性顺序为:(苄基,溴乙基)(甲基,乙基,丙基,丁基)乙烯基;当3位为对氯苯基取代时,其整体活性顺序为:(乙烯基,苄基)(甲基,乙基,丙基,丁基)。结论:为了得到更好的抗肿瘤活性化合物,吡咯母核的1号位置上应该接入苄基等大空间位阻基团、容易形成氢键的基团或者不接入任何取代基,从而为吡咯类化合物的进一步结构修饰以开发更高活性的抗肿瘤化合物提供指导。     

谷氨酸棒状杆菌异源合成萜类化合物的研究进展

萜类化合物具有可观的商业价值,但生产过程复杂,产量低,利用微生物异源合成萜类化合物已成为热点。谷氨酸棒状杆菌内含合成萜类色素的途径,具有异源合成萜类化合物的天然优势和研究前景。首次对谷氨酸棒状杆菌合成萜类化合物进行了综述,从萜类合成途径、关键酶和全局调控机制三个方面进行了途经介绍。概述了谷氨酸棒状杆菌中单萜、倍半萜、四萜类化合物的异源合成,并对利用谷氨酸棒状杆菌高效合成萜类化合物所需解决的问题进行讨论,为谷氨酸棒状杆菌高效合成萜类化合物提供建议。     

应用生物法合成内酯化合物

内酯是广泛存在于自然界中具有生物活性的一类化合物。由于大多数内酯化合物具有手性,用化学方法合成不仅过程复杂,而且产率也不高。利用酶反应的特异性,应用生物法合成内酯化合物具有很好的应用前景,其中包括微生物次生代谢合成内酯,脂肪酸生物转化合成内酯和脂肪酶在有机相中催化羟基脂肪酸形成内酯。本文报道这些领域的进展。     

假蒟叶的生物碱类成分研究

研究假蒟(Piper sarmentosum)叶的化学成分及其对金黄色葡萄球菌的抑菌活性。采用正相硅胶柱、Sephadex LH-20凝胶柱和半制备高效液相色谱等分离技术,从假蒟叶的总生物碱部位分离得到7个生物碱类成分,结合化合物的理化性质和波谱学数据,分别鉴定为chaplupyrrolidone C(1)、chaplupyrrolidone A(2)、chaplupyrrolidone B(3)、假蒟酰胺A(4)、N-3-苯丙酰胺吡咯(5)、3-(4-羟基-3,5-二甲氧基苯基)丙酰胺吡咯(6)、3-(3,4,5-三甲氧基苯基)丙酰胺吡咯(7)。其中,化合物1为新的酰胺类生物碱,化合物7为首次从假蒟中分离得到。采用微量二倍稀释法测试所有分离化合物的抑菌活性,结果表明化合物1～4对金黄色葡萄球菌均具有不同程度的抑制作用。     

α-酮酸及其盐的合成研究进展

α-酮酸及其盐是一类双官能团化合物,是重要的有机合成、药物合成及生物合成中间体,在医药和化工等行业有重要的应用前景.本文综述了α-酮酸及其盐的合成研究进展,着重介绍了近年来合成α-酮酸及其盐的几种方法.主要有羰基化法、格氏试剂法、氨基酸氧化法和海因法等,同时展望了α-酮酸及其盐的应用前景.     

酿酒酵母合成异源单萜类化合物的研究进展

单萜类化合物在食品、医药和工业等领域有重要的应用,具有可观的经济价值.随着合成生物学的日益发展,利用微生物作为细胞工厂合成单萜类化合物成为时下的研究热点.酿酒酵母是真核生物表达的模式菌株,其甲羟戊酸途径为单萜类化合物的合成提供直接前体,因此在酿酒酵母中构建异源单萜类化合物合成途径有较大优势.本文介绍了酿酒酵母细胞中异源单萜类化合物合成途径的构建.从甲羟戊酸途径代谢通量调控机制和融合酶调控酶催化反应效率两方面概述了酿酒酵母异源合成单萜类化合物的研究进展.     

伯氏致病杆菌SN52中的二硫吡咯类物质及其生物活性

在我们从天然产物中寻找新抗菌剂的过程中,利用硅胶柱层析、凝胶柱层析和半制备高效液相色谱技术从昆虫病原线虫共生菌Xenorhabdus bovienii SN52的发酵液中分离得到6个单体化合物,通过波普综合解析和文献数据对照对分离到的单体化合物进行结构鉴定。结果显示,均为二硫吡咯类物质,其中化合物1和2为新化合物,4个已知化合物分别鉴定为Xenorhabdin I(3)、Xenorhabdin II(4)、Xenorhabdin IV(5)、Xenorhabdin V(6)。使用微量肉汤稀释法测试化合物1~6的抗菌活性,其结构-活性关系表明二硫吡咯衍生物的抗菌活性受到侧链的可变取代基的显著影响。     

Redox status affects the catalytic activity of glutamyl-tRNA synthetase

Glutamyl-tRNA synthetases (GluRS) provide Glu-tRNA for different processes including protein synthesis, glutamine transamidation and tetrapyrrole biosynthesis. Many organisms contain multiple GluRSs, but whether these duplications solely broaden tRNA specificity or also play additional roles in tetrapyrrole biosynthesis is not known. Previous studies have shown that GluRS1, one of two GluRSs from the extremophile Acidithiobacillus ferrooxidans, is inactivated when intracellular heme is elevated suggesting a specific role for GluRS1 in the regulation of tetrapyrrole biosynthesis. We now show that, in vitro, GluRS1 activity is reversibly inactivated upon oxidation by hemin and hydrogen peroxide. The targets for oxidation-based inhibition were found to be cysteines from a SWIM zinc-binding motif located in the tRNA acceptor helix-binding domain. tRNA^Glu was able to protect GluRS1 against oxidative inactivation by hemin plus hydrogen peroxide. The sensitivity to oxidation of A. ferrooxidans GluRS1 might provide a means to regulate tetrapyrrole and protein biosynthesis in response to extreme changes in both the redox and heme status of the cell via a single enzyme.     

Recent advances in production of 5-aminolevulinic acid using biological strategies

5-Aminolevulinic acid (5-ALA) is the precursor for the biosynthesis of tetrapyrrole compounds and has broad applications in the medical and agricultural fields. Because of the disadvantages of chemical synthesis methods, microbial production of 5-ALA has drawn intensive attention and has been regarded as an alternative in the last years, especially with the rapid development of metabolic engineering and synthetic biology. In this mini-review, recent advances on the application and microbial production of 5-ALA using novel biological approaches (such as whole-cell enzymatic-transformation, metabolic pathway engineering and cell-free process) are described and discussed in detail. In addition, the challenges and prospects of synthetic biology are discussed.     

Post-translational control of tetrapyrrole biosynthesis in plants, algae, and cyanobacteria

The tetrapyrrole biosynthetic pathway provides the vital cofactors and pigments for photoautotrophic growth (chlorophyll), several essential redox reactions in electron transport chains (haem), N- and S-assimilation (sirohaem), and photomorphogenic processes (phytochromobilin). While the biochemistry of the pathway is well understood and almost all genes encoding enzymes of tetrapyrrole biosynthesis have been identified in plants, the post-translational control and organization of the pathway remains to be clarified. Post-translational mechanisms controlling metabolic activities are of particular interest since tetrapyrrole biosynthesis needs adaptation to environmental challenges. This review surveys post-translational mechanisms that have been reported to modulate metabolic activities and organization of the tetrapyrrole biosynthesis pathway.     

Tetrapyrrole‐based drought stress signalling

Tetrapyrroles such as chlorophyll and heme play a vital role in primary plant metabolic processes such as photosynthesis and respiration. Over the past decades, extensive genetic and molecular analyses have provided valuable insights into the complex regulatory network of the tetrapyrrole biosynthesis. However, tetrapyrroles are also implicated in abiotic stress tolerance, although the mechanisms are largely unknown. With recent reports demonstrating that modified tetrapyrrole biosynthesis in plants confers wilting avoidance, a component physiological trait to drought tolerance, it is now timely that this pathway be reviewed in the context of drought stress signalling. In this review, the significance of tetrapyrrole biosynthesis under drought stress is addressed, with particular emphasis on the inter‐relationships with major stress signalling cascades driven by reactive oxygen species (ROS) and organellar retrograde signalling. We propose that unlike the chlorophyll branch, the heme branch of the pathway plays a key role in mediating intracellular drought stress signalling and stimulating ROS detoxification under drought stress. Determining how the tetrapyrrole biosynthetic pathway is involved in stress signalling provides an opportunity to identify gene targets for engineering drought‐tolerant crops.     

Microbiological synthesis of tetrapyrrole compounds

This paper reviews publications on the biosynthesis of functional tetrapyrroles by microorganisms. Emphasis is given to the structure of uroporphyrin III methylated derivatives termed corriphyrins and their involvement in the formation of two groups of tetrapyrrole pigments--corrinoids and siroheme. Current concepts concerning the final stages of the formation of the corrine ring and potential cobalt-free precursors of vitamin B12 are discussed. It is indicated that the data available may help elucidate evolutionary and biogenetic patterns in the emergence and interaction of tetrapyrrole compounds and formulate problems of practical importance.     

Biosynthesis of open-chain tetrapyrroles in Prochlorococcus marinus

Members of the genus Prochlorococcus belong to the most abundant phytoplankton on earth. In contrast to other cyanobacteria, Prochlorococcus is characterized by divinyl-chlorophyll containing light-harvesting complexes and the lack of phycobilisomes. Despite the lack of phycobilisomes, all sequenced genomes of Prochlorococcus possess genes that putatively encode enzymes involved in the biosynthesis of open-chain tetrapyrrole molecules. Here, biochemical evidence is presented indicating that high-light- and low-light-adapted Prochlorococcus ecotypes possess genes encoding functional enzymes for the biosynthesis of open-chain tetrapyrrole molecules. Experiments on recombinant protein as well as through complementation studies of a cyanobacterial insertion mutant revealed the functionality of the bilin reductases investigated.     

Interaction of the molecular chaperone HtpG with uroporphyrinogen decarboxylase in the cyanobacterium Synechococcus elongatus PCC 7942

Uroporphyrinogen decarboxylase (HemE) is important due to its location at the first branch-point in tetrapyrrole biosynthesis. We detected a complex formation between full-length polypeptides of HtpG and HemE by biochemical studies in vivo and in vitro. The interaction suppressed the enzyme activity, suggesting a regulatory role of HtpG in tetrapyrrole biosynthesis.