Triterpenoids are one of the most diverse compounds in plant metabolites, and they have a wide variety of physiological activities and are of important economic value. Oxidosqualene cyclases catalyze the cyclization of 2, 3-oxidosqualene to generate different types of sterols and plant triterpenoids, which is of great significance to the structural diversity of natural products. However, the mechanism of the diversified cyclization of 2, 3-oxidosqualene catalyzed by oxidosqualene cyclases remains unclear. This review summarized the research progress of oxidosqualene cyclases from the aspects of catalytic function, molecular evolutionary relationship between genes and proteins, protein structure, molecular simulation and molecular calculations, which may provide a reference for protein engineering and metabolic engineering of triterpene cyclase.
Intramolecular Transferases/metabolism* ; Metabolic Engineering ; Plants/genetics* ; Squalene/chemistry* ; Triterpenes

Lanosterol synthase( LS) is a key enzyme involving in the mevalonate pathway( MVA pathway) to produce lanosterol,which is a precursor of ganoderma triterpenoid. And the transcriptional regulation of LS gene directly affects the content of triterpenes in Ganoderma lucidum. In order to study the transcriptional regulation mechanism of LS gene,yeast one-hybrid technique was used to screen the transcription regulators which interact withthe promoter of LS. The bait vector was constructed by LS promoter,then the vector was transformed yeast cells to construct bait yeast strain. One-hybrid c DNA library was constructed via SMART technology. Then the c DNA and p GADT7-Rec vector were co-transformed into the bait yeast strain to screen the upstream regulatory factors of the promoter region of LS by homologous recombination. Total of 23 positive clones were screened. After sequencing,blast was performed against the whole-genome sequence of G. lucidum. As a result,8 regulatory factors were screened out including the transcription initiation TFIIB,the alpha/beta hydrolase super family,ALDH-SF superfamily,60 S ribosomal protein L21,ATP synthase β-subunit,microtubule associated protein Cript,prote asome subunit β-1,and transaldolase. Until now,the regulation effect of these 8 regulatory factors in G.lucidum has not been reported. This study provides candidate proteins for in-depth study on the expression regulation of LS.
Gene Library ; Intramolecular Transferases/metabolism* ; Reishi/genetics* ; Saccharomyces cerevisiae ; Transcription Factors/metabolism*

OBJECTIVETo analyze the correlation between content of glycyrrhizic acid and the single nucleotide polymorphism of beta-amyrin synthase (bAS) in Glycyrrhiza uralensis.

METHODglycyrrhizic acid content in 80 samples of the cultivated G. uralensis were determined by HPLC; According to the very significant level (P < 0.000 1), 80 samples in accordance with glycyrrhizic acid will be grouped by SAS 9.0; Using RT-PCR strategy to amplification the Open Reading Frame of beta-amyrin synthase with the template of total RNA extracted from roots of G. uralensis and then using DNAman to analyze the relationship between glycyrrhizic acid content and the single nucleotide polymorphism of beta-amyrin synthase (bAS).

RESULTThere exited two mutation sites 94 bp and 254 bp, G/A conversion occurred at 94 bp site, which belonged to a missense mutation. G/A conversion led to the corresponding amino acid conversion (Gly --> Asp); C/T conversion occurred at 254 bp site, which belonged to a synonymous mutation. According to sequence variation, the samples were divided into four genotypes: G-T genotype, A-T genotype, G/A-C genotype and G-T genotype.

CONCLUSIONA-T genotype, G/A-C genotype and G-T genotype are correlated with the high content of glycyrrhizic acid.

Genotype ; Glycyrrhiza uralensis ; enzymology ; genetics ; metabolism ; Glycyrrhizic Acid ; metabolism ; Intramolecular Transferases ; genetics ; Polymorphism, Single Nucleotide ; Reproducibility of Results

In this study, the synthetic pathway of β-amyrin was constructed in the pre-constructed Saccharomyces cerevisiae chassis strain Y0 by introducing β-amyrin synthase from Glycyrrhiza uralensis, resulting strain Y1-C20-6, which successfully produced β-amyrin up to 5.97 mg·L~(-1). Then, the mevalonate pyrophosphate decarboxylase gene(ERG19), mevalonate kinase gene(ERG12), 3-hydroxy-3-methylglutaryl-CoA synthase gene(ERG13), phosphomevalonate kinase gene(ERG8) and IPP isomerase gene(IDI1)were overexpressed to promoted the metabolic fluxto the direction of β-amyrin synthesis for further improving β-amyrin production, resulting the strain Y2-C2-4 which produced β-amyrin of 10.3 mg·L~(-1)under the shake flask fermentation condition. This is 100% higher than that of strain Y1-C20-6, illustrating the positive effect of the metabolic engineering strategy applied in this study. The titer of β-amyrin was further improved up to 157.4 mg·L~(-1) in the fed-batch fermentation, which was almost 26 fold of that produced by strain Y1-C20-6. This study not only laid the foundation for the biosynthesis of β-amyrin but also provided a favorable chassis strain for elucidation of cytochrome oxidases and glycosyltransferases of β-amyrin-based triterpenoids.
Fermentation ; Glycyrrhiza uralensis ; enzymology ; genetics ; Industrial Microbiology ; Intramolecular Transferases ; genetics ; Metabolic Engineering ; Oleanolic Acid ; analogs & derivatives ; biosynthesis ; Saccharomyces cerevisiae ; metabolism

Glycyrrhiza uralensis Fisch. ex DC is widely used in traditional Chinese medicine (TCM). Among its various active components, glycyrrhizic acid is believed to be the marker component. Squalene synthase (SQS) and beta-amyrin synthase (beta-AS) are key enzymes in the biosynthetic pathway of glycyrrhizic acid in G uralensis. To reveal the effects of co-expression of SQS1 and beta-AS genes on this pathway, 7 yeast expression vectors harboring different SQS1 variants and beta-AS were constructed and expressed in Saccharomyces cerevisiae as fusion proteins. TLC and GC-MS results showed that co-expression of SQS1 and beta-AS enhanced the accumulation of beta-amyrin. The effects of SQS12 were more obvious than the other two SQS1 variants. This study is significant for further investigations concerned with exploring the biosynthesis of glycyrrhizic acid in vitro and strengthening the efficacy of G. uralensis by means of increasing the content of glycyrrhizic acid.
Farnesyl-Diphosphate Farnesyltransferase ; genetics ; metabolism ; Glycyrrhiza uralensis ; genetics ; Intramolecular Transferases ; metabolism ; Oleanolic Acid ; analogs & derivatives ; metabolism ; Plant Proteins ; genetics ; Recombinant Proteins ; metabolism ; Saccharomyces cerevisiae ; metabolism

OBJECTIVETo clone and sequence the open reading frame of beta-amyrin synthase (bAS) from Glycyrrhiza uralensis.

METHODThe primers were designed according to the cDNA sequence of beta-amyrin synthase from G. glabra reported by Hiroaki HAYASHI, and the open reading frame of beta-amyrin synthase was cloned by RT-PCR strategy with the template of total RNA extracted from roots of G. uralensis.

RESULTThe GubAS (GenBank Accession number: FJ627179) was 2 289 bp in length encoding one pelypeptide of 762 amino acid. Deduced amino acid sequence had 99%, 92%, 90%, 90% and 89% homology to the amino acid sequence of G. glabra, Lotus japonicus, Pisum sativum, Medicago truncatula, Glycine max, respectively.

CONCLUSIONThe open reading frame of bAS from G. uralensis is cloned and reported for the first time. The conclusion will provide a foundation for exploring the mechanism of triterpenes biosynthesis.

Cloning, Molecular ; Glycyrrhiza uralensis ; classification ; enzymology ; genetics ; Intramolecular Transferases ; genetics ; metabolism ; Molecular Sequence Data ; Open Reading Frames ; Phylogeny ; Plant Proteins ; genetics ; metabolism ; Plants ; classification ; genetics

The cyclization of 2,3-oxidosqualene is the key branch point of ergosterol and triterpenoid biosynthesis. Downregulation of 2,3-oxidosqualene metabolic flux to ergosterol in Saccharomyces cerevisiae may redirect the metabolic flux toward the triterpenoid synthetic pathway. In our study, primers were designed according to erg7 gene sequence of S. cerevisiae. Three fragments including 5' long fragment, 5' short fragment and erg7 coding region fragment were amplified by PCR. 5' long fragment consists of the promoter and a part of erg7 coding region sequence. 5' short fragment consists of a part of promoter and a part of erg7 coding region sequence. These fragments were inserted reversely into pESC-URA to construct antisense expression plasmids. The recombinant plasmids were transformed into S. cerevisiae INVSc1 and recombinant strains were screened on the nutritional deficient medium SD-URA. The erg7 expression level of recombinant strains, which harbored antisense expression plasmid of erg7 coding region, was similar to that of INVScl by semi-quantitative PCR detection. But erg7 expression level of recombinant strains, which harbored 5' long antisense fragment and 5' short antisense fragment, was significantly lower than that of the control. The results of TLC and HPLC showed that the ergosterol content of recombinant strains, which harbored 5' long antisense fragment, decreased obviously. The ergosterol contents of the others were almost equal to that of INVSc1. Lanosterol synthase gene expression was downregulated by antisense RNA technology in S. cerevisiae, which lays a foundation for reconstructing triterpenoid metabolic pathway in S. cerevisiae by synthetic biology technology.
DNA Primers ; Down-Regulation ; Gene Expression ; Intramolecular Transferases ; genetics ; metabolism ; Plasmids ; Polymerase Chain Reaction ; RNA, Antisense ; Saccharomyces cerevisiae ; enzymology ; genetics ; Squalene ; analogs & derivatives ; metabolism ; Transformation, Genetic

Lanosterol synthase is encoded by the erg7 gene and catalyzes the cyclization of 2, 3-oxidosqualene, which is a rate-limiting step of the inherent mevalonate (MVA)/ergosterol metabolic pathway in Saccharomyces cerevisiae. The intermediate 2, 3-oxidosqualene is also the precursor of triterpenoids. Therefore, the cyclization of 2, 3-oxidosqualene is the key branch point of ergosterol and triterpenoids biosynthesis. Down-regulation of 2, 3-oxidosqualene metabolic flux to ergosterol in S. cerevisiae may redirect the metabolic flux toward the triterpenoid synthetic pathway reconstructed by the synthetic biology approach. To construct erg7 knockout cassette harboring the loxP-Marker-loxP element, long primers were designed, which were homologous to the sequences of both erg7 ORF and plasmid pUG66. The cassette was transformed into diploid wild strain INVSc1 by LiAc/SS Carrier DNA/PEG method and then erg7 gene haploid deficient mutant was obtained by homologous recombination. The results of semiquantitative PCR and real-time quantitative PCR revealed that erg7 expression level in erg7 gene haploid deficient mutant is one time lower than that in wild strain. The results of TLC and HPLC showed that the ergosterol content in deficient mutant decreased to 42% of that in wild strain.
Chromatography, High Pressure Liquid ; DNA Primers ; Down-Regulation ; Ergosterol ; metabolism ; Haploidy ; Intramolecular Transferases ; genetics ; Polymerase Chain Reaction ; Saccharomyces cerevisiae ; genetics ; Squalene ; analogs & derivatives ; metabolism

OBJECTIVETo clone and sequence the open reading frame of cycloartenol synthase (CAS) from Huperzia carinata.

METHODAfter searching the transcriptome dataset of H. carinata, one unique sequence containing oxide squalene cyclases domain was discovered. The primers were designed according to the cDNA sequence of CAS from the dataset. And then, the open reading frame of CAS was cloned by RT-PCR strategy with the template of mixed RNA extracted from root, stem and leaf of H. carinata. The bioinformatic analysis of this gene and its corresponding protein was performed.

RESULTOne unique sequence of CAS, named as HcCAS1 (GenBank accession number JN790125) , was cloned from H. carinata. The open reading frame of HcCAS1 consists of 2 474 bp, encoding one polypeptide with 757 amino acids.

CONCLUSIONThis study cloned and analyzed CAS from H. carinata for the first time. The result will provide a foundation for exploring the mechanism of sterol biosynthesis in Huperziaceae plants.

Amino Acid Sequence ; Cloning, Molecular ; Computational Biology ; Evolution, Molecular ; Huperzia ; enzymology ; genetics ; Intramolecular Transferases ; chemistry ; genetics ; metabolism ; Models, Molecular ; Molecular Sequence Data ; Phylogeny ; Protein Structure, Secondary

Blakeslea trispora CarRA has both lycopene cyclase and phytoene synthase activity. In order to analyze the double functional activity of CarRA proteins and to detect the active sites of lycopene cyclase, we constructed two detection systems in Escherichia coli by color complementary. Through PCR-driven overlap extension we got carRA gene cDNA, then constructed prokaryotes expression vector pET28a-carRA. pET28a-carRA with plasmid pAC-LYC carrying crtl/crtB/crtE gene clusters were co-transformed to BL21(DE3) to validate lycopene cyclase activity. We constructed the plasmid pAC-LYC delta (crtB) carrying crtl/crtE gene clusters, then co-transtormed them with pET28a-carRA to BL21(DE3) to validate phytoene synthase activity. Based on color complementary, and HPLC analysis of metabolites, we confirmed that the CarRA protein activity detection system was reliable. Our study provides a screening model for specific mutation of lycopene cyclase without affecting phytoene synthase activity.
Alkyl and Aryl Transferases ; genetics ; metabolism ; Carotenoids ; biosynthesis ; Cloning, Molecular ; DNA, Complementary ; genetics ; Escherichia coli ; genetics ; metabolism ; Fungal Proteins ; genetics ; metabolism ; Genetic Vectors ; genetics ; Geranylgeranyl-Diphosphate Geranylgeranyltransferase ; Intramolecular Lyases ; genetics ; metabolism ; Mucorales ; enzymology ; genetics ; Mutation ; Polymerase Chain Reaction