Generation of 'Unnatural Natural Product' library and identification of a small molecule inhibitor of XIAP

Natural products have been utilized for drug discovery. To increase the source diversity, we generated a new chemical library consisting of chemically modified microbial metabolites termed 'Unnatural Natural Products' by chemical conversion of microbial metabolites in crude broth extracts followed by purification of reaction products with the LC-photo diode array-MS system. Using this library, we discovered an XIAP inhibitor, C38OX6, which restored XIAP-suppressed enzymatic activity of caspase-3 in vitro. Furthermore, C38OX6 sensitized cancer cells to anticancer drugs, whereas the unconverted natural product did not. These findings suggest that our library could be a useful source for drug seeds.     

Enzyme inhibitors of microbial origin

The screening for enzyme inhibitors of microbial origin in the past decades has been a prosperous area to find new metabolites that are of potential importance as therapeutic or antibiotic agents. This review attempts a survey of recent achievements in this type of screening. Special emphasis is given to enzyme inhibitors and screening systems in fields where industry has a main interest in development. This includes some notes on the improved methodology for the detection of reversible and irreversible inhibitors of beta-lactamases and the presentation of a unique inhibitor of alpha-amylase from porcine pancreas isolated from a strain of Streptomyces tendae. This inhibitor (HOE 467) may be of potential use in the treatment of diabetic conditions, obesity and adipositas. The results show that the screening for enzyme inhibitors from microorganisms still provides one of the central challenges for future research.     

Formylation and acetylation of 4-chloroaniline by a Streptomyces sp.

4-Chloroaniline was metabolized in a liquid growth medium by a Streptomyces sp. which was isolated from soil. After 60 gours of incubation the aniline had disappeared and several metabolites could be detected by thin layer chromatographic analysis. 4-Chloroformylaniline and 4-chloroacetanilide were identified as products. The formation of a formylanilide by the actinomycete indicates a new mechanism of microbial aniline transformation.     

Rapid identification of elaiophylin and geldanamycin inStreptomyces fermentation broths using CPC coupled with a photodiode array detector and LC-MS methodologies

During the course of screening microbial broth extracts in various high through-put bioassays (eg receptor binding or enzyme inhibition), several actinomycete cultures were discovered to produce active metabolites. The natural products elaiophylin and/or geldanamycin are produced by severalStreptomyces violaceusniger strains, and the bioactivity of the extracts from these cultures was frequently associated with the fractions containing these metabolites. CPC coupled to a photodiode array detector and LC-MS techniques were applied to these broth extracts to ascertain rapidly when these natural products were present. These methodologies allowed us to identify the metabolites quickly in the crude extract, and the application demonstrated further the utility of CPC-photodiode array detection and LC-MS as powerful, initial analytical tools in analyses of the complex metabolite profiles produced by microorganisms.     

Mycolic acid-containing bacteria induce natural-product biosynthesis in Streptomyces species

Natural products produced by microorganisms are important starting compounds for drug discovery. Secondary metabolites, including antibiotics, have been isolated from different Streptomyces species. The production of these metabolites depends on the culture conditions. Therefore, the development of a new culture method can facilitate the discovery of new natural products. Here, we show that mycolic acid-containing bacteria can influence the biosynthesis of cryptic natural products in Streptomyces species. The production of red pigment by Streptomyces lividans TK23 was induced by coculture with Tsukamurella pulmonis TP-B0596, which is a mycolic acid-containing bacterium. Only living cells induced this pigment production, which was not mediated by any substances. T. pulmonis could induce natural-product synthesis in other Streptomyces strains too: it altered natural-product biosynthesis in 88.4% of the Streptomyces strains isolated from soil. The other mycolic acid-containing bacteria, Rhodococcus erythropolis and Corynebacterium glutamicum, altered biosynthesis in 87.5 and 90.2% of the Streptomyces strains, respectively. The coculture broth of T. pulmonis and Streptomyces endus S-522 contained a novel antibiotic, which we named alchivemycin A. We concluded that the mycolic acid localized in the outer cell layer of the inducer bacterium influences secondary metabolism in Streptomyces, and this activity is a result of the direct interaction between the mycolic acid-containing bacteria and Streptomyces. We used these results to develop a new coculture method, called the combined-culture method, which facilitates the screening of natural products.     

内生放线菌对鬼臼毒素的微生物转化

调查桃儿七根茎内生放线菌对鬼臼毒素的微生物转化,以期获得一些鬼臼毒素的结构类似物或衍生物。利用表面消毒法分离内生放线菌;采用薄层层析和高效液相色谱(HPLC)方法筛选转化鬼臼毒素的内生放线菌;利用硅胶柱层析和制备HPLC分离纯化生物转化产物;应用波谱技术解析转化产物的化学结构;通过形态学、生理生化特征和16S rRNA基因序列分析对内生放线菌进行初步鉴定。从桃儿七根茎中分离出20株内生放线菌,经筛选发现其中1株放线菌能转化鬼臼毒素,其产物为4’-去甲基表鬼臼毒素。初步鉴定该内生放线菌为Streptomyces sp.。内生放线菌Streptomyces sp.能对鬼臼毒素进行去甲基和异构化修饰,推测其可能具有O-去甲基化酶和异构化酶。     

Degradation of vanillic acid and production of guaiacol by microorganisms isolated from cork samples

The presence of guaiacol in cork stoppers is responsible for some cases of cork taint causing unpleasant alterations to wine. We have performed a characterization of the cork-associated microbiota by isolating 55 different microorganisms: eight yeast, 14 filamentous fungi or molds, 13 actinomycetes and 20 non-filamentous bacteria. A screening for degradation of vanillic acid and guaiacol production showed that none of the filamentous fungi could achieve any of these processes. By contrast, five of the eight yeast strains isolated were able to degrade vanillic acid, although it was not converted to guaiacol. Guaiacol production was only detected in four bacterial strains: one isolate of Bacillus subtilis and three actinomycetes, Streptomyces sp. A3, Streptomyces sp. A5 and Streptomyces sp. A13, were able to accumulate this compound in both liquid media and cultures over cork. These results suggest that guaiacol-mediated cork taint should be attributed to the degradative action of vanillic acid by bacterial strains growing on cork.     

一株海洋链霉菌MMHS020的抗菌活性代谢产物

【背景】海洋微生物因其生存环境的多样性与独特性,已成为天然产物研究的重要来源。【目的】以一株太平洋海泥来源链霉菌MMHS020为出发菌株,筛选可促进其产生丰富代谢产物的发酵条件,挖掘菌株在抗菌抗肿瘤方面的潜力。【方法】采用单菌株多次级代谢产物策略对MMHS020菌株进行培养诱导,使其产生更丰富的活性代谢产物。双层平板法测定发酵产物对6种指示菌的抑菌活性。以硅胶柱层析、葡聚糖凝胶层析和制备层析等方法对代谢产物进行分离纯化,再通过质谱技术和~1H-NMR和~(13)C-NMR对化合物进行结构解析。【结果】链霉菌属MMHS020菌株可在较高浓度盐离子环境中产生丰富的抑菌活性代谢产物,显示出对枯草芽孢杆菌、结核分枝杆菌和藤黄微球菌等多种指示菌的抑制活性。从发酵产物中分离鉴定了3个化合物,分别是诺卡胺素(1)、麦角甾醇(2)和星形孢菌素(3)。其中星形孢菌素表现出白色念珠菌的抑制活性,而诺卡胺素则对其他几个指示菌表现出较强的抑制活性。【结论】海洋链霉菌MMHS020菌株可代谢产生丰富多样的生物活性物质,具有开发成为新型抑菌生物制剂的潜力。     

Alpha-glucosidase inhibitors of microbial origin]

The data on spreading of inhibitors of alpha-glucosidases with microbial origin are given. Physiochemical characteristics of acorbose--a known inhibitor of alpha-glucosidases--and new inhibitor isolated from Streptomyces sp. are given in detail.     

A novel extracellular subtilisin inhibitor produced by a Streptomyces sp

The amino acid composition and inhibitory properties of a protein (SI-1-72) isolated from the culture medium of a Streptomyces sp. have been investigated. SI-1-72 appears to be a monomer protein of molecular mass about 13,100 Da and amino acid composition which differs from that of the inhibitors of the Streptomyces subtilisin inhibitor (SSI) family. Furthermore, it was found to exhibit novel specificity: strong inhibitory effect against microbial alkaline proteinases, moderate effect towards chymotrypsin and elastase, and no inhibition of the other serine proteinases, as well as of the cysteine, aspartate and metallo-proteinases.     

Isolation and Physiological Activities of Piericidin A,A Natural Insecticide Produced by Streptomyces

In the course of screening research on new insecticides among metabolites of microorganisms, two active components were isolated from mycellia of Streptomyces sp. 16–22. The names, Piericidin A and B, were proposed to these active metabolites. Isolation procedure, physical and chemical properties and physiological activities of Piericidin A were presented. From the results of taxonomic study on Streptomyces sp. 16–22, it was found that this is a new species, to which the name, Streptomyces mobaraensis Nagatsu et Suzuki, was proposed.     

Microbiological transformations of delta6a10a-tetrahydrocannabinol.

A screening program was conducted to find microorganisms that catalyze transformation reactions with cannabinoids. Three hundred fifty-eight cultures, consisting of 97 bacteria, 175 actinomycetes, and 86 molds, were incubated in media containing 0.5 mg of Delta(6a,10a)-tetrahydrocannabinol (Delta(6a,10a)-THC) per ml. After 120 h of cultivation, ethyl acetate extracts of the cultures were examined by thin-layer chromatography (TLC) for transformation products. About 18% of the cultures modified Delta(6a,10a)-THC. The ability to modify the substrate did not predominate among any particular group of microorganisms. After purification, the products from three cultures were analyzed by high-resolution mass spectrometry, 100-mHz proton magnetic resonance spectrometry, ultraviolet spectrometry, and infrared spectrometry. These spectral data indicated that a Mycobacterium sp. oxidized Delta(6a,10a)-THC to cannabinol and a diastereomeric pair of 6a-hydroxy-Delta(10,10a)-THC isomers; a Streptomyces sp. and a Bacillus sp. oxidized Delta(6a,10a)-THC to 7-keto-Delta(6a,10a)-THC and 4'-hydroxy-Delta(6a,10a)-THC, respectively. The occurrence of these products and the presence of others that have not yet been isolated or identified indicate that microbial transformation may be a useful tool for the preparation of new cannabinoids that have desirable pharmacological properties.     

Artificial chromosomes for antibiotic-producing actinomycetes

Bacteria belonging to the order Actinomycetales produce most microbial metabolites thus far described, several of which have found applications in medicine and agriculture. However, most strains were discovered by their ability to produce a given molecule and are, therefore, poorly characterized physiologically and genetically. Thus, methodologies for genetic manipulation of actinomycetes are not available and efficient tools have been developed for just a few strains. This constitutes a serious limitation to applying molecular genetics approaches to strain development and structural manipulation of microbial metabolites. To overcome this hurdle, we have developed bacterial artificial chromosomes (BAC) that can be shuttled among Escherichia coli, where they replicate autonomously, and a suitable Streptomyces host, where they integrate site-specifically into the chromosome. The existence of gene clusters and of genetically amenable host strains, such as Streptomyces coelicolor or Streptomyces lividans, makes this a sensible approach. We report here that 100 kb segments of actinomycete DNA can be cloned into these vectors and introduced into genetically accessible S. lividans, where they are stably maintained in integrated form in its chromosome.     

Detection of novel secondary metabolites.

The study of antibiotics and other fermentation products has shown that a seemingly unlimited number of compounds with diverse structures are produced by microorganisms. The continued high rate of discovery of new chemical entities, in the light of the abundance of microbial products already described, is due to creative screening procedures that incorporate such features as the emphasis on unusual microorgnaisms, their special propagation and fermentation requirements, supersensitive and highly selective assays, genetic engineering both for the biosynthesis of new compounds and in the development of screening systems, early in vivo evaluation, improved isolation techniques, modern procedures for structure determination, computer-assisted identification, and an efficient multidisciplinary approach. This review focuses on the genesis and development of the gamut of methodologies that have led to the successful detection of the wide variety of novel secondary metabolites that include antibacterial, antigungal, antiviral and antitumour antibiotics, enzyme inhibitors, pharmacologically and immunologically active agents, products useful in agriculture and animal husbandry, microbial regulators, and other compounds for which no bioactive role has yet been found.     

广西北部湾放线菌的分离筛选及活性产物的鉴定

为从广西北部湾的泥样和植物中分离海洋放线菌,筛选具有抑菌活性的菌株,分离活性化合物。研究采用普通稀释法分离菌株,对发酵产物进行抑菌活性测试,利用活性追踪分离活性化合物,并通过波谱方法确定化合物结构。结果表明从6个海泥样品和3个植物样品中共分离73株放线菌,筛选得到具有抑香蕉枯萎病和金黄色葡萄球菌活性的菌株7株,并从其中的1株链霉菌 Streptomyces sp.MDCW-126的次级代谢产物中分离鉴定了星形孢菌素。从广西北部湾分离的药用活性菌株资源具有开发和深入研究价值。     

Draft genome sequence of marine Streptomyces sp. strain W007, which produces angucyclinone antibiotics with a benz[a]anthracene skeleton

A series of angucyclinone antibiotics have been isolated from marine Streptomyces sp. strain W007 and identified. Here, a draft genome sequence of Streptomyces sp. W007 is presented. The genome contains an intact biosynthetic gene cluster for angucyclinone antibiotics, which provides insight into the combinatorial biosynthesis of angucyclinone antibiotics produced by marine streptomycetes.     

微生物肽类次级代谢产物研究进展

微生物肽类次级代谢产物是一类重要的天然产物,因含有稀有氨基酸而具有丰富的化学结构和生物活性。随着微生物天然产物分离纯化技术的发展,新型肽类产物层出不穷,在微生物次级代谢产物的研究领域扮演了重要的角色。本文综述近年来发现的来自细菌和真菌的微生物肽类代谢产物,以及采用基因挖掘等手段人工合成的新型肽类产物,并结合近年来本团队昆虫病原线虫共生菌肽类产物的研究积累,分析微生物肽类产物研究存在的问题及可能的解决方案,以期为微生物导向的新型活性肽类产物的深入发掘和应用研究提供参考。     

Genistein, a soy isoflavone, is a potent alpha-glucosidase inhibitor.

Genistein is an isoflavone that is known to be contained in soybean. It was proved that genistein plays a pivotal role in homeostasis in the human body. In the course of screening for useful alpha-glucosidase inhibitors, we isolated and identified genistein as a candidate for alpha-glucosidase inhibitor from fermentation broths of a Streptomyces sp. Genistein was shown to be a reversible, slow-binding, non-competitive inhibitor of yeast alpha-glucosidase with a K(i) value of 5.7x10(-8) M when the enzyme mixture was pretreated with genistein. These results show a possibility that genistein could be a useful tool for metabolic disorders.     

Advances in drug discovery and biochemical studies

Japanese researchers continue to discover new means to combat parasites and make important contributions toward developing tools for global control of parasitic diseases. Streptomyces avermectinius, the source of ivermectin, was discovered in Japan in the early 1970s and renewed and vigorous screening of microbial metabolites in recent years has led to the discovery of new antiprotozoals and anthelminthics, including antimalarial drugs. Intensive studies of parasite energy metabolism, such as NADH-fumarate reductase systems and the synthetic pathways of nucleic acids and amino acids, also contribute to the identification of novel and unique drug targets.     

Streptomyces sp. 173, an insecticidal micro-organism from marine

AIMS: To find new insecticidal antibiotics from marine micro-organisms. METHODS AND RESULTS: Strains isolated from seawater and sea sediments from Beidiahe and Dagang of the east coast of China were screened for their insecticidal qualities. The screening was carried out using bioassay of brine shrimp and the insect pest Helicoverpa armigera. The fermentation, preliminary extraction and isolation of Streptomyces sp.173 were carried out. CONCLUSIONS: In total 331 isolates were examined through bioassay of brine shrimp and 40 isolates (12.08%) showed potential insecticidal activities. Of the 40 isolates, one isolate, designated Streptomyces sp.173, was found to have strong insecticidal activity against both brine shrimp and H. armigera, similar to that of avermectin B1. SIGNIFICANCE AND IMPACT OF THE STUDY: The isolated Streptomyces sp.173 has great insecticidal potency. This work indicated that marine micro-organisms could be an important source of insecticidal antibiotics and the improved anti-brine shrimp bioassay is suitable for primary screening.