Advances in the microbial synthesis of aromatic fragrance molecules / 生物工程学报

Aromatic compounds make up a large part of fragrances and are traditionally produced by chemical synthesis and direct extraction from plants. Chemical synthesis depends on petroleum resources and has disadvantages such as causing environment pollutions and harsh reaction conditions. Due to the low content of aromatic compounds in plants and the low yield of direct extraction, plant extractions require large amounts of plant resources that occupy arable land. In recent years, with the development of metabolic engineering and synthetic biology, microbial synthesis of aromatic compounds from renewable resources has become a promising alternative approach to traditional methods. This review describes the research progress on the synthesis of aromatic fragrances by model microorganisms such as Escherichia coli or yeast, including the synthesis of vanillin through shikimic acid pathway and the synthesis of raspberry ketone through polyketide pathway. Moreover, this review highlights the elucidation of native biosynthesis pathways, the construction of synthetic pathways and metabolic regulation for the production of aromatic fragrances by microbial fermentation.

Advances in metabolic engineering for the production of aromatic chemicals / 生物工程学报

Metabolic engineering has been developed for nearly 30 years since the early 1990s, and it has given a great impetus to microbial strain breeding and improvement. Aromatic chemicals are a variety of important chemicals that can be produced by microbial fermentation and are widely used in the pharmaceutical, food, feed, and material industry. Microbial cells can be engineered to accumulate a variety of useful aromatic chemicals in a targeted manner through rational engineering of the biosynthetic pathways of shikimate and the derived aromatic amino acids. This review summarizes the metabolic engineering strategies and biosynthetic pathways for the production of aromatic chemicals developed in the past 30 years, with the aim to provide a valuable reference and promote the research in this field.

Using dynamic molecular switches for shikimic acid production in Escherichia coli / 生物工程学报

Shikimic acid is an intermediate metabolite in the synthesis of aromatic amino acids in Escherichia coli and a synthetic precursor of Tamiflu. The biosynthesis of shikimic acid requires blocking the downstream shikimic acid consuming pathway that leads to inefficient production and cell growth inhibition. In this study, a dynamic molecular switch was constructed by using growth phase-dependent promoters and degrons. This dynamic molecular switch was used to uncouple cell growth from shikimic acid synthesis, resulting in the production of 14.33 g/L shikimic acid after 72 h fermentation. These results show that the dynamic molecular switch could redirect the carbon flux by regulating the abundance of target enzymes, for better production.

Shikimic Acid Promotes Oligodendrocyte Precursor Cell Differentiation and Accelerates Remyelination in Mice / 神经科学通报·英文版

The obstacle to successful remyelination in demyelinating diseases, such as multiple sclerosis, mainly lies in the inability of oligodendrocyte precursor cells (OPCs) to differentiate, since OPCs and oligodendrocyte-lineage cells that are unable to fully differentiate are found in the areas of demyelination. Thus, promoting the differentiation of OPCs is vital for the treatment of demyelinating diseases. Shikimic acid (SA) is mainly derived from star anise, and is reported to have anti-influenza, anti-oxidation, and anti-tumor effects. In the present study, we found that SA significantly promoted the differentiation of cultured rat OPCs without affecting their proliferation and apoptosis. In mice, SA exerted therapeutic effects on experimental autoimmune encephalomyelitis (EAE), such as alleviating clinical EAE scores, inhibiting inflammation, and reducing demyelination in the CNS. SA also promoted the differentiation of OPCs as well as their remyelination after lysolecithin-induced demyelination. Furthermore, we showed that the promotion effect of SA on OPC differentiation was associated with the up-regulation of phosphorylated mTOR. Taken together, our results demonstrated that SA could act as a potential drug candidate for the treatment of demyelinating diseases.

Lipid-lowering effect of seven traditional Chinese medicine monomers in zebrafish system / 生理学报

The present study aimed to study lipid-lowering effect of seven traditional Chinese medicine monomers in zebrafish system. Zebrafish were fed with high fat diet to establish a hyperlipemia model, then fasted and bathed with seven traditional Chinese medicine monomers stigmasterol, triacontanol, chrysophanol, vanillic acid, shikimic acid, polydatin and oleanolic acid respectively. The oil red O staining was used to detect the blood lipids of zebrafish. Serum total cholesterol and triglyceride levels were detected to validate the lipid-lowering effect. The result showed that a zebrafish model of hyperlipemia could be established by feeding larvae zebrafish with high fat diet. Among the seven traditional Chinese medicine monomers, chrysophanol had lipid-lowering effect. Chrysophanol significantly reduced serum total cholesterol and triglyceride levels in adult zebrafish fed with high fat diet. Chrysophanol accelerated peristalsis frequency of zebrafish intestine and the excretion of high fat food. It is concluded that chrysophanol has lipid- lowering effect in zebrafish, and the mechanism of the effect may be due to the roles of chrysophanol in reducing lipid absorption from gastrointestinal tract and accelerating the excretion of food.

Enhanced production of shikimic acid using a multi-gene co-expression system in Escherichia coli / 中国天然药物

Shikimic acid (SA) is the key synthetic material for the chemical synthesis of Oseltamivir, which is prescribed as the front-line treatment for serious cases of influenza. Multi-gene expression vector can be used for expressing the plurality of the genes in one plasmid, so it is widely applied to increase the yield of metabolites. In the present study, on the basis of a shikimate kinase genetic defect strain Escherichia coli BL21 (ΔaroL/aroK, DE3), the key enzyme genes aroG, aroB, tktA and aroE of SA pathway were co-expressed and compared systematically by constructing a series of multi-gene expression vectors. The results showed that different gene co-expression combinations (two, three or four genes) or gene orders had different effects on the production of SA. SA production of the recombinant BL21-GBAE reached to 886.38 mg·L(-1), which was 17-fold (P < 0.05) of the parent strain BL21 (ΔaroL/aroK, DE3).

Cloning and expression analysis of a hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferasegene(IiHCT) from Isatis indigotica / 中国中药杂志

Based on the transcriptome data, we cloned the open reading frame of IiHCT gene from Isatis indigotica, and then performed bioinformatic analysis of the sequence. Further, we detected expression pattern in specific organs and hairy roots treated methyl jasmonate( MeJA) by RT-PCR. The IiHCT gene contains a 1 290 bp open reading frame( ORF) encoding a polypeptide of 430 amino acids. The predicted isoelectric point( pI) was 5.7, a calculated molecular weight was about 47.68 kDa. IiHCT was mainly expressed in stem and undetectable in young root, leaf and flower bud. After the treatment of MeJA, the relative expression level of IiHCT increased rapidly. The expression level of IiHCT was the highest at 4 h and maintained two fold to control during 24 h. In this study, cloning of IiHCT laid the foundation for illustrating the biosynthesis mechanism of phenylpropanoids in I. indigotica.

Improving 3-dehydroshikimate production by metabolically engineered Escherichia coli / 生物工程学报

In the aromatic amino acid biosynthetic pathway 3-dehydroshikimate (DHS) is a key intermediate. As a potent antioxidant and important feedstock for producing a variety of important industrial chemicals, such as adipate and vanillin, DHS is of great commercial value. Here, in this study, we investigated the effect of the co-expression of aroFFBR (3-deoxy-D-arabino-heptulosonate 7-phosphate synthase mutant with tyrosine feedback-inhibition resistance) and tktA (Transketolase A) at different copy number on the production of DHS. The increased copy number of aroFFBR and tktA would enhance the production of DHS by the fold of 2.93. In order to further improve the production of DHS, we disrupted the key genes in by-product pathways of the parent strain Escherichia coli AB2834. The triple knockout strain of ldhA, ackA-pta and adhE would further increase the production of DHS. The titer of DHS in shake flask reached 1.83 g/L, 5.7-fold higher than that of the parent strain E. coli AB2834. In 5-L fed-batch fermentation, the metabolically engineered strain produced 25.48 g/L DHS after 62 h. Metabolically engineered E. coli has the potential to further improve the production of DHS.

Rational design and construction of an overproducing shikimic acid Escherichia coli by metabolic engineering / 生物工程学报

Shikimic acid (SA), as a hydroaromatic intermediate in the common pathway of aromatic amino acid biosynthesis, is the starting material for the synthesis of neuraminidase inhibitors and other useful compounds. The fermentative production of SA by metabolically engineered microorganisms is an excellent alternative to the extraction from fruits of the Illicium plant. In this study, Escherichia coli was metabolically engineered by rational design and genetic manipulation for fermentative production of SA. Firstly, blocking the aromatic amino acid pathway after the production of SA was carried out by deletion of aroL and aroK genes encoding SA kinase. Secondly, the ptsG gene encoding protein EIICBglc were removed in the aroL/aroK mutant strain to make the phosphotransferase system (PTS) system default. In the resulting strain, the phosphoenolpyruvate-dependent PTS pathway, a main pathway for glucose transport, were replaced by ATP-dependent GalP (galactose permease). Thus, more PEP flux was used to produce SA as a critical precursor of SA. Furthermore, ydiB gene (encoding quinic acid/SA dehydrogenase) was deleted to prevent SA precursors of 3-dehyroquinic acid into the byproduct of quinic acid. Thus, the engineered strain with four genes deletion was constructed and 576 mg/L SA was produced in the shake flask fermentation. Results show that SA produciton was increased 90 times compared to the parent strain E. coli CICIM B0013.

Determination of plasma protein binding rate of isopropylidene-shikimic acid / 中国中药杂志

<p><b>OBJECTIVE</b>To study the plasma protein binding rate of isopropylidene-shikimic acid.</p><p><b>METHOD</b>The ultrafiltration was employed to determine the plasma protein binding rate of isopropylidene-shikimic acid. The plasma concentrations of isopropylidene-shikimic acid were measured by HPLC.</p><p><b>RESULT</b>The plasma protein binding rate of isopropylidene-shikimic acid with dog plasma at the concentration of 0.3, 0.15 g x L(-1) and 0.5 mg x L(-1) were (4.36 +/- 0.02)%, (4.12 +/- 0.19)% and (2.23 +/- 0.59)%, respectively. While the plasma protein binding rate of isopropylidene-shikimic acid with normal human plasma at the above concentrations were (11.23 +/- 0.01)%, (10.06 +/- 0.69)% and (9.72 +/- 0.59)%, respectively.</p><p><b>CONCLUSION</b>The binding rate of isopropylidene-shikimic acid with plasma protein is low.</p>

Fungal and Plant Phenylalanine Ammonia-lyase

L-Phenylalanine is one of the essential amino acids that cannot be synthesized in mammals in adequate amounts to meet the requirements for protein synthesis. Fungi and plants are able to synthesize phenylalanine via the shikimic acid pathway. L-Phenylalanine, derived from the shikimic acid pathway, is used directly for protein synthesis in plants or metabolized through the phenylpropanoid pathway. This phenylpropanoid metabolism leads to the biosynthesis of a wide array of phenylpropanoid secondary products. The first step in this metabolic sequence involves the action of phenylalanine ammonia-lyase (PAL). The discovery of PAL enzyme in fungi and the detection of 14CO2 production from 14C-ring-labeled phenylalanine and cinnamic acid demonstrated that certain fungi can degrade phenylalanine by a pathway involving an initial deamination to cinnamic acid, as happens in plants. In this review, we provide background information on PAL and a recent update on the presence of PAL genes in fungi.

Monitoramento do ácido chiquímico no manejo de plantas daninhas com glifosato em pomar comercial de citros / Shikimic acid monitoring in weed control with glyphosate in a commercial citrus orchard

Com o objetivo de verificar o acúmulo de ácido chiquímico em plantas de laranja pêra (Citrus sinensis) num pomar comercial manejado com glifosato, um herbicida sistêmico de amplo espectro, foram coletadas amostras na Fazenda Jequitibá, tradicional no cultivo de citros, situada no Município de Santo Antônio de Posse, SP. O produtor aplicou de forma convencional Roundup® Original a 1.440 g.ha-1 de equivalente ácido (e.a.) do sal de isopropilamino de glifosato em 19/12/ 2006 na entrelinha de 15 plantas, deixando outras cinco como testemunha. A reaplicação de glifosato a 1.260 g.ha-1 de e.a. foi realizada em 2/4/2007. Em ambos os casos, imediatamente antes da aplicação e aos 3, 7, 10, 15, 20 e 35 dias após, foram coletadas 20 folhas de cada planta tanto da área tratada como da não tratada, analisando-se o teor de ácido chiquímico por cromatografia líquida de alta eficiência (CLAE) de forma isocrática após extração por micro-ondas. Os resultados mostraram não ocorrer acúmulo do ácido chiquímico nas plantas de laranja pêra, não havendo diferenças significativas nos teores deste composto entre o material proveniente da área tratada com glifosato e o daquela capinada manualmente.

In order to check the accumulation of shikimic acid in a traditional commercial grove of citrus "Pêra" cultivar (Citrus sinensis) managed for weed control with glyphosate, a systemic herbicide with wide spectrum, samples were collected at Fazenda Jequitibá, in Santo Antonio de Posse County, São Paulo State, Brazil. The producer applied the following treatments of Roundup Original® glyphosate at 1,440 g.ha-1 a.e. of the isopropylamine salt on 19 December 2006 between rows of 15 plants, leaving five others as control. The reapplication of glyphosate at 1,260 g ha-1 was done on 2 April 2007. In both cases, immediately before application and at 3, 7, 10, 15, 20 and 35 days thereafter, 20 leaves from each treated and untreated plants were collected for analysis of the content of shikimic acid by isocratic high performance liquid chromatography (HPLC) assisted with microwave. The results showed no significant differences in levels of shikimic acid between the material from the area treated with glyphosate and that weeded manually.

Two new sesquiterpene lactones from the pericarp of Illicium macranthum / 药学学报

Silica gel column chromatography was used for the isolation and purification of the chemical constituents of the pericarp of Illicium macranthum. From dichloromethane-EtOAc (1:1) fraction and EtOAc fraction of the methanol extracts, eleven compounds were identified on the basis of chemical and spectral data. Two new compounds were elucidated to be 6-deoxyneomajucin (1) and 2-oxo-6-deoxyneomajucin (2), along with nine known compounds 6-deoxypseudoanisatin (3), pseudoanisatin (4), anisatin (5), pseudomajucin (6), protocatecheuic acid (7), shikimic acid (8), shikimic acid methylester (9), beta-sitosterol (10) and daucosterol (11). Compounds 1 and 2 are new majucin-type sesquiterpene lactones.

Chemical constituents from Sarcandra glabra / 中国中药杂志

<p><b>OBJECTIVE</b>To study the chemical constituents of the plant of Sarcandra glabra and provide reference for the study of the bioactive substances.</p><p><b>METHOD</b>The compounds were isolated from the EtOH extract by various chromatographic methods and their structures were elucidated by their physico-chemical properties and the analysis of their spectral data.</p><p><b>RESULT</b>Nine compounds were isolated and identified as isoscopletin (1), syringaresinol monoside (2), styraxjaponoside B (3), 5-O-caffeoylshikimic acid (4), shizukanolide E (5), isoastilbin (6), neoisoastilbin (7), astilbin (8), neoastilbin (9).</p><p><b>CONCLUSION</b>Compounds 1-7 were isolated from S. glabra for the first time.</p>

Studies on chemical constituents from leaves of Sapium sebiferum / 中国中药杂志

<p><b>OBJECTIVE</b>To study the chemical constituents from leaves of Sapium sebiferum.</p><p><b>METHOD</b>The compounds were isolated and purified by silic gel column chromatography and preparative HPLC. The structures were identified by various spectral evidence.</p><p><b>RESULT</b>Nine compounds were obtained and they were shikimic acid (1), kaempferol (2), quercetin (3), isoquercein (4), hyperin (5), kaempferol-3-O-beta-D-glucopyranoside (6), kaempferol-3-O-beta-D-glueopyranoside (7), gallic acid (8), rutin (9).</p><p><b>CONCLUSION</b>Compounds 1, 5, 6 and 7 are isolated from this genus for the first time and compound 9 is isolated from this plant for the first time.</p>

The changes of rare codon and mRNA structure accelerate expression of qa-3 in Escherichia coli / 生物工程学报

The key and crucial step of metabolic engineering during quinic acid biosynthesize using shikimic acid pathway is high expression of quinate 5-dehydrogenase. The gene qa-3 which code quinate 5-dehydrogenase from Neurospora crassa doesn't express in Escherichia coli. By contrast with codon usage in Escherichia coli, there are 27 rare codons in qa-3, including eight AGG/AGA (Arg) and nine GGG (Gly). Two AGG are joined together (called box R) and some GGG codons are relative concentrate (called box G). Along with the secondary structure of mRNA analysed in computer, the free energy of mRNA changes a lot from -374.3 kJ/mol to least -80.5 kJ/mol when some bases in the end of qa-3 were transformed, and moreover, the change of free energy is quite small when only some bases in the box G and box R transformed. After the change of rare codon and optimization of some bases in the end, qa-3 was expression in E. coli and also the enzyme activity of quinate 5-dehydrogenase can be surveyed accurately. All the work above benefit the further research on producing quinic acid engineering bacterium.

The isolation and identification of a new lignanoside from Selaginella tamariscina (Beauv.) Spring / 药学学报

<p><b>AIM</b>To study the chemical constituents of Selaginella tamariscina (Beauv.) Spring.</p><p><b>METHODS</b>The compounds were isolated and purified by macroporous adsorption resin, Sephadex LH-20 and silica gel column chromatography and identified on the basis of their physicochemical and spectral data.</p><p><b>RESULTS</b>Four compounds were obtained from the n-BuOH fraction of 70% acetone extracts. Their structures were elucidated as (7S, 8R)-7, 8-dihydro-7-(4-hydroxy-3,5-dimethoxyphenyl)-8-hydroxymethyl-[1'-( 7'-hydroxyethyl)-5' methoxyl] benzofuran-4-O-beta-D-glucopyranoside (tamariscinoside C, I), D-mannitol (II), tyrosine (II), shikimic acid (IV).</p><p><b>CONCLUSION</b>Compound I is a new compound, compounds II and III were obtained from the genius for the first time, compound IV was yielded from the plant for the first time.</p>

Protective effect of 3,4-oxo-isopropylidene-shikimic acid on vascular endothelial cell injured by hydrogen peroxide / 药学学报

<p><b>AIM</b>To study the effect of 3,4-oxo-isopropylidene-shikimic acid (ISA) on H2O2 (200 mol.L-1, 4 h) injured human umbilical vein endothelial cells (HUVEC).</p><p><b>METHODS</b>Morphological change was observed under microscop. Cell viability was assessed by MTT assay. The release of intracellular lactate dehydrogenase (LDH) and NO was assessed by colorimetry. Radioimmunoassay was used to assess 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha).</p><p><b>RESULTS</b>Pretreatment with ISA for 6 h alleviated the morphological damage of H2O2 induced HUVECs. At the concentration of 1-100 mumol.L-1, ISA prevented the inhibitory effect on cell viability induced by H2O2 in dose-dependent manner, but increased the ratio of cell viability from 60.4% to 84.3%. ISA reduced LDH release and increased the level of NO and 6-keto-PGF1 alpha in H2O2 induced HUVECs.</p><p><b>CONCLUSION</b>ISA exerted protective effect on H2O2 injured HUVEC.</p>

Experimental studies on the anti-thrombosis effect of 3,4-oxo-isopropylidene-shikimic acid / 药学学报

<p><b>AIM</b>To study the effect of 3,4-oxo-isopropylidene-shikimic acid (ISA) against arteriovenous shunt and middle cerebral artery thrombosis (MCAT) in rats.</p><p><b>METHODS</b>Arteriovenous shunt model was adopted to measure thrombus weight; The neurologic deficit (ND) and the infarct size (IS) of the middle cerebral thrombosis (MCAT) model induced by FeCl3 were observed; The effect of ISA on platelet aggregation rate of rat and rabbit by giving ISA in vivo and in vitro was studied.</p><p><b>RESULTS</b>ISA 25, 50, 100 and 200 mg.kg-1 ig was shown to reduced the weight of thrombus in arteriovenous shunt model; ISA 50, 100 and 200 mg.kg-1 ig for 2 times in 24 hours, attenuated the ND of rats subjected to MCAT; ISA 100 and 200 mg.kg-1 reduced IS of rats after MCAT by 27.8% and 31.6%, respectively; ISA 50, 100 and 200 mg.kg-1 ig inhibited platelet aggregation of normal rats; ISA 10(-3)-10(-5) mol.L-1, inhibited rabbit platelet aggregation in vitro.</p><p><b>CONCLUSION</b>ISA inhibited thrombosis by anti-platelet-aggregation.</p>