Probing the Deoxyflavonoid Biosynthesis: Naringenin Chalcone Is a Substrate for the Reductase Synthesizing Isoliquiritigenin.

Isoliquiritigenin formation is a key reaction during deoxyflavonoid biosynthesis, which is catalyzed by two enzymes, chalcone synthase (CHS) and reductase (CHR). The substrates for CHS are established. However, the substrate for CHR is unknown.

Recombinant yeast as a functional tool for understanding bitterness and cucurbitacin biosynthesis in watermelon (Citrullus spp.).

Cucurbitacins are a group of bitter-tasting oxygenated tetracyclic triterpenes that are produced in the family Cucurbitaceae and other plant families. The natural roles of cucurbitacins in plants are probably related to defence against pathogens and pests. Cucurbitadienol, a triterpene synthesized from oxidosqualene, is the first committed precursor to cucurbitacins produced by a specialized oxidosqualene cyclase termed cucurbitadienol synthase.

Cyclization of all-E- and 2Z-geranylfarnesols by a bacterial triterpene synthase: insight into sesterterpene biosynthesis in Aleuritopteris ferns.

Aleuritopteris ferns produce triterpenes and sesterterpenes with tricyclic cheilanthane and tetracyclic 18-episcalarane skeletons. The structural and mechanistic similarities between both classes of fern terpene suggest that their biosynthetic enzymes may be closely related. We investigate here whether a triterpene synthase is capable of recognizing geranylfarnesols as a substrate, and is able to convert them to cyclic sesterterpenes.

Antimicrobial polyacetylenes from Panax ginseng hairy root culture.

Two new polyacetylenes, 1-hydroxydihydropanaxacol (3) and 17-hydroxypanaxacol (4), were isolated from Panax ginseng hairy root culture, along with dihydropanaxacol (1), panaxacol (2) and ginsenoyne D (5). Highly hydroxylated compounds 1-4 were isolated from the medium and compound 5, which was a biosynthetic precursor of compound 1, was isolated from the roots. Compounds 1-4 showed antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Cryptococcus neoformans and Aspergillus fumigatus.

Identification and characterization of glycosyltransferases involved in the biosynthesis of soyasaponin I in Glycine max.

Triterpene saponins are a diverse group of compounds with a structure consisting of a triterpene aglycone and sugars. Identification of the sugar-transferase involved in triterpene saponin biosynthesis is difficult due to the structural complexity of triterpene saponin. Two glycosyltransferases from Glycine max, designated as GmSGT2 and GmSGT3, were identified and characterized.

Molecular evolution of fern squalene cyclases.

Triterpenes, a diverse group of natural products comprising six isoprene units, are distributed across various organisms from bacteria to higher plants. Ferns are sporophytes that produce triterpenes and are lower on the evolutionary scale than higher plants. Among ferns that produce triterpenes analogous to bacterial hopanoids, Polypodiodes niponica produces migrated dammaranes and oleananes, which are also widely found in higher plants.

Protostadienol synthase from Aspergillus fumigatus: functional conversion into lanosterol synthase.

Oxidosqualene:protostadienol cyclase (OSPC) from the fungus Aspergillus fumigatus, catalyzes the cyclization of (3S)-2,3-oxidosqualene into protosta-17(20)Z,24-dien-3beta-ol which is the precursor of the steroidal antibiotic helvolic acid. To shed light on the structure-function relationship between OSPC and oxidosqualene:lanosterol cyclase (OSLC), we constructed an OSPC mutant in which the C-terminal residues (702)APPGGMR(708) were replaced with (702)NKSCAIS(708), as in human OSLC. As a result, the mutant no longer produced the protostadienol, but instead efficiently produced a 1:1 mixture of lanosterol and parkeol.

Biosynthesis of steroidal antibiotic fusidanes: functional analysis of oxidosqualene cyclase and subsequent tailoring enzymes from Aspergillus fumigatus.

Three putative oxidosqualene cyclase (OSC) genes exist in the genome of the fungus Aspergillus fumigatus that produces a steroidal antibiotic, helvolic acid. One of these genes, Afu4g14770, designated AfuOSC3, is clustered with genes of cytochrome P450 monooxygenases (P450s), a short-chain dehydrogenase/reductase (SDR), and acyltransferases, which presumably function in triterpene tailoring steps, suggesting that this gene cluster codes for helvolic acid biosynthesis. AfuOSC3 was PCR amplified from A.

Identification of a product specific beta-amyrin synthase from Arabidopsis thaliana.

Triterpene skeletons are produced by oxidosqualene cyclases (OSCs). The genome sequencing of Arabidopsis thaliana revealed the presence of thirteen OSC homologous genes including At1g78950, which has been revised recently as two independent ORFs, namely At1g78950 and At1g78955. The cDNA corresponding to the revised At1g78950 was obtained by RT-PCR, ligated into Saccharomyces cerevisiae expression vector pYES2, and expressed in a lanosterol synthase deficient S.

Biosynthesis of baccharis oxide, a triterpene with a 3,10-oxide bridge in the A-ring.

A new oxidosqualene cyclase (OSC) cDNA was cloned from the roots of Stevia rebaudiana. Functional expression in yeast and spectral analyses of the products established that the obtained OSC yields baccharis oxide as the major product. This is the first identification of an OSC yielding baccharis oxide.

Dammaradiene synthase, a squalene cyclase, from Dryopteris crassirhizoma Nakai.

Ferns produce a variety of cyclic triterpene hydrocarbons in large amount. Squalene cyclases (SCs) are responsible enzymes for formation of cyclic triterpene hydrocarbon skeletons. Although more than ten bacterial SCs have been cloned and four of them characterized for their enzymatic products, the only example of a fern SC is ACH, from Adiantum capillus-veneris, which produces hydroxyhopane.

Squalene cyclase and oxidosqualene cyclase from a fern.

Ferns are the most primitive vascular plants. The phytosterols of ferns are the same as those of higher plants, but they produce characteristic triterpenes. The most distinct feature is the lack of oxygen functionality at C-3, suggesting that the triterpenes of ferns may be biosynthesized by direct cyclization of squalene.

Production of triterpene acids by cell suspension cultures of Olea europaea.

Olive (Olea europaea) contains large quantity of triterpene acids including oleanolic acid (6) as a major one. Varieties of biological activities exhibited by triterpene acids attracted our attentions, especially from pharmaceutical viewpoints. Cell culture of olive plant was induced and its triterpene constituents were studied.

Origin of structural diversity in natural triterpenes: direct synthesis of seco-triterpene skeletons by oxidosqualene cyclase.

At1g78500, one of the oxidosqualene cyclase (OSC) homologues from Arabidopsis thaliana, was expressed in a lanosterol synthase-deficient yeast strain and the products were analyzed. In addition to the known triterpenes, this OSC was found to produce two new triterpenes, the structures of which were determined by NMR and MS analyses. The new triterpenes are C-ring-seco-beta-amyrin (1) and C-ring-seco-alpha-amyrin (2) and named beta-seco-amyrin and alpha-seco-amyrin, respectively.

Stereochemical course in water addition during LUP1-catalyzed triterpene cyclization.

Arabidopsis thaliana LUP1 (At1g78970) catalyzes the cyclization of oxidosqualene into lupeol and 3beta,20-dihydroxylupane (lupanediol). The stereochemical course of water addition to the lupanyl cation was studied. The X-ray crystal structure of lupanylepoxide 3,5-dinitrobenzoate established the configuration of epoxide as 20S.

Molecular cloning and functional expression of a multifunctional triterpene synthase cDNA from a mangrove species Kandelia candel (L.) Druce.

Homology based PCRs with degenerate primers designed from the conserved sequences among the known oxidosqualene cylases (OSCs) have resulted in cloning of a triterpene synthase (KcMS) from the young roots of Kandelia candel (L.) Druce (Rhizophoraceae). KcMS consists of a 2286 bp open reading frame, which codes for 761 amino acids.

Dammarenediol-II synthase, the first dedicated enzyme for ginsenoside biosynthesis, in Panax ginseng.

Panax ginseng produces triterpene saponins called ginsenosides, which are classified into two groups by the skeleton of aglycones, namely dammarane type and oleanane type. Dammarane-type ginsenosides dominate over oleanane type not only in amount but also in structural varieties. However, their sapogenin structure is restricted to two aglycones, protopanaxadiol and protopanaxatriol.

A new triterpene synthase from Arabidopsis thaliana produces a tricyclic triterpene with two hydroxyl groups.

[structure: see text] Thirteen oxidosqualene cyclase homologues exist in the genome of Arabidopsis thaliana. One of these genes, At4g15340, was amplified by PCR and expressed in yeast. The yeast transformant accumulated tricyclic triterpene, (3S,13R)-malabarica-17,21-dien-3,14-diol (arabidiol), whose structure was determined by NMR and MS analyses.

Lanosterol synthase in dicotyledonous plants.

Sterols are important as structural components of plasma membranes and precursors of steroidal hormones in both animals and plants. Plant sterols show a wide structural variety and significant structural differences from those of animals. To elucidate the origin of structural diversity in plant sterols, their biosynthesis has been extensively studied [Benveniste (2004) Annu.

Identification of beta-amyrin and sophoradiol 24-hydroxylase by expressed sequence tag mining and functional expression assay.

Triterpenes exhibit a wide range of structural diversity produced by a sequence of biosynthetic reactions. Cyclization of oxidosqualene is the initial origin of structural diversity of skeletons in their biosynthesis, and subsequent regio- and stereospecific hydroxylation of the triterpene skeleton produces further structural diversity. The enzymes responsible for this hydroxylation were thought to be cytochrome P450-dependent monooxygenase, although their cloning has not been reported.

Revised structures of epohelmins A and B isolated as lanosterol synthase inhibitors from a fungal strain FKI-0929.

The structures of epohelmins A and B isolated as lanosterol synthase inhibitors from a fungal strain FKI-0929 were revised to be 1 alpha-hydroxy-3alpha-(4'-oxoundec-(5' E)-enyl)-pyrrolizidine and 1beta-hydroxy-3 alpha-(4'-oxoundec-(5 'E)-enyl)-pyrrolizidine, respectively, by comparison with spectral data of synthetic compounds.

Two O-methyltransferases isolated from flower petals of Rosa chinensis var. spontanea involved in scent biosynthesis.

Rosa chinensis var. spontanea predominantly emits 1,3,5-trimethoxybenzene together with methyleugenol and isomethyleugenol as minor floral scent compounds. Two O-methyltransferases (OMTs), designated as RcOMT1 and RcOMT2, were isolated from rose flower petals using homology-based screening strategies.

Inhibition of human lanosterol synthase by the constituents of Colocasia esculenta (taro).

Ethanol extracts of lyophilized vegetables were tested for inhibition of human lanosterol synthase (hOSC) in order to find the compounds to suppress cholesterol biosynthesis. Of 130 samples tested, twelve samples showed significant inhibition. Among them, Colocasia esculenta (taro) showed the highest inhibition (55% inhibition at 300 microg/ml).

Synthesis of digalactosyl diacylglycerols and their structure-inhibitory activity on human lanosterol synthase.

Digalactosyl and monogalactocyl diacylglycerols (DGDG and MGDG), which were identified as anti-hyperlipemia active components in Colocasia esculenta (Taro), were synthesized. The inhibitory activity of DGDG, MGDG and related compounds on human lanosterol synthase was evaluated as anti-hyperlipemic activity. DGDG with two myristoyl groups at both sn-1 and sn-2 positions and with an oleoyl group at the sn-1 position showed the most potent activity.

Epohelmins A and B, novel lanosterol synthase inhibitors from a fungal strain FKI-0929.

From a fungal strain FKI-0929, two compounds designated epohelmins A and B, were isolated as new natural products with inhibitory activity against recombinant human lanosterol synthase. The crude extract from the whole broth of this strain was fractionated by silica gel column chromatography and HPLC to afford two isolated inhibitors. Detailed spectroscopic analyses led to the identification of their structures.