A recombinant cyclodextrin glycosyltransferase cloned from Paenibacillus sp. strain RB01 showed improved catalytic activity in coupling reaction between cyclodextrins and disaccharides

Recombinant cyclodextrin glycosyltransferase (CGTase) was obtained by cloning the PCR gene fragment from thermotolerant Paenibacillus sp. strain RB01 screened from hot spring area in Thailand and cloned into the Escherichia coli expression vector. The nucleotide sequence was analyzed and aligned. Nucleotide sequence of the recombinant CGTase contained an open reading frame of 2139 bp encoding 713 amino acid residues. The recombinant required one-third of culture time and neutral pH to produce CGTase compared to wild type. CGTases from both wild type and transformant were purified in parallel by starch adsorption and DEAE cellulose column. Their biochemical properties such as molecular weight, optimum pH and temperature were quite similar. However, the recombinant enzyme showed improved catalytic activity in the coupling reaction between cyclodextrins (CDs) and some disaccharides. Among several sugars tested with excess βCD, cellobiose was the best substrate followed by leucrose. Very low activity was observed with trehalose, lactose and mellibiose. Sucrose and raffinose showed no activity. The K _m and other kinetic parameters of recombinant enzyme were determined for cellobiose and several cyclodextrin derivatives. Recombinant CGTase showed lower K _m for βCD and its derivatives, with improved activity compared to wild type enzyme.     

Characterization of cyclodextrin glycosyltransferase from Bacillus firmus strain No. 37

The enzyme cyclod extringly cosyltransferase (CGTase), EC2.4.1.19, which produces cyclodextrins (CDs) from starch, was obtained from Bacillus firmus strain no. 37 isolated from Brazilian soil and characterized in the soluble form using as substrate 100 g/L of maltodextrin in 0.05 M Tris-HCl buffer, 5 mM CaCl₂, and appropriate buffers. Enzymatic activity and its activation energy were determined as a function of temperature and pH. The activation energy for the production of β- and γ-CD was 7.5 and 9.9 kcal/mol, respectively. The energy of deactivation was 39 kcal/mol. The enzyme showed little thermal deactivation in the temperature range of 35–60°C, and Arrhenius-type equations were obtained for calculating the activity, deactivation, and half-life as a function of temperature. The molecular weight of the enzyme was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, giving 77.6k Da. Results for CGTase activity as a function of temperature gave maximal activity for the production of β-CD at 65°C, pH 6.0, and 7 1.5 mmol of β-CD/(min·mg of protein), whereas for γ-CD it was 9.1 m mol of γ-CD/(min·mg of protein) at 70°C and pH 8.0. For long contact times, the bestuse of the enzymatic activity occurs at 60°C oratalower temperature, and the reaction pH may be selected to increase the vield of a desired CD.     

Glycosylidene Carbenes. Part 6. Synthesis of alkyl and fluoroalkyl glycosides

The syntheses of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolytic conditions are described. Yields and diastereoselectivities depend upon the pK_HA values of the alcohols, the solvent, and the reaction temperature. The glycosidation of weakly acidic alcohols (MeOH, EtOH, i-PrOH, and t-BuOH, 1 equiv. each) in CH₂Cl₂ at room temperature leads to the glycosides 2–5 in yields between 60 and 34% (Scheme 1 and Table 1). At ?70 to ?60°, yields are markedly higher. In CH₂Cl₂, diastereoselectivities are very low. In THF, at ?70 to ?60°, however, glycosidation of i-PrOH leads to α-D -/β-D - 4 in a ratio of 8:92. More strongly acidic alcohols, such as CF₃CH₂OH, (CF₃)₂ CHOH, and (CF₃)₂C(Me)OH, and the highly fluorinated long-chain alcohols CF₃(CF₂)₅(CH₂)₂OH ( 11 ) and CHF₂(CF₂)₉CH₂OH ( 13 ) react (CH₂Cl₂, r.t.) in yields between 73 and 85% and lead mainly to the β-D -glucosides β-D - 6 to β-D - 8 , β-D - 12 , and β-D - 14 (d.e. 14–68%). Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2-dimetoxyethane, or THF are used, as examined for the glycosidation of (CF₃)₂C(Me)OH, yielding (1,2-dimethoxyethane, 25°) 80% of α-D -/ β-D - 8 in a ratio of 2:98 (d.e. 96%; Table 4). In EtCN, (CF₃)₂C(Me)OH yields up to 55% of the imidate 10 . Glycosidation of di-O-isopropylideneglucose 15 leads to 16 (CH₂Cl₂, r.t.; 65%, α-D / β-D = 33:67). That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10 , derived from the attack of (CF₃)₂MeCO^? on an intermediate nitrilium ion (Scheme 4), and for weakly acidic alcohols, by the formation of α-D - 9 and β-D - 9 , derived by attack of i-PrO^? on intermediate tetrahydrofuranylium ions. A working hypothesis is presented (Scheme 3). The diastereoselectivities are rationalized on the basis of a protonation in the σ plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnO? C(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO^? in the π plane of the (solvated) oxonium ion.     

Biochemical properties and cyclodextrin production profiles of isoforms of cyclodextrin glycosyltransferase

Cyclodextrin glycosyltransferase (CGTase) catalyzes the conversion of starch to cyclodextrin (CD), an important host molecule for the study of host?Cguest interactions. CGTase from Paenibacillus sp. RB01 and its recombinant form showed the same isoform pattern. The three isoforms, two major (isoforms I and II) and one minor (isoform III), all had a different net charge but the same molecular mass. The aim of this work was to characterize the three isoforms, and especially to compare their CD production profiles. Isoforms I and II were separated on a FPLC Mono Q column and showed the same optimum pH (pH 5 for dextrinizing and pH 6?C7 for cyclization activity) and optimum temperature (65?C70 °C for both activities). However, the two isoforms differed in their catalytic efficiency of the coupling reaction with variable concentrations of the ??-CD donor in the presence of a fixed amount of cellobiose acceptor, with k_cat/K_m values of 3.46 × 10^?3 and 2.20 × 10^?3 mM^?1 min^?1, for isoforms I and II, respectively. Both isoforms I and II were found to have ??-CGTase activity and gave a similar CD6:CD7:CD8 product ratio of 0.2:1.0:0.6, with an increase in the ratio of the small-ring to the large-ring CDs from 1.0:0.5 to 1.0:0.3 from a 6 to 24 h reaction time. However, in terms of maximal CD yields, the two isoforms differed in their optimal reaction temperature and time required, the optimal conditions being at 40 °C for 6 h for isoform I and at 60 °C for 24 h for isoform II.     

Enzymatic approach to unnatural glycosides with diverse aglycon scaffolds using glycosyltransferase VinC

Glycosyltransferase VinC was explored for a construction of glycoside libraries using dTDP-vicenisamine and structurally unrelated unnatural aglycons, and new unnatural vicenisaminides were successfully constructed. Structural elements of aglycon recognition by VinC were proposed by modeling studies and were confirmed by the success of transglycosylation upon a designed aglycon.     

New triterpene glycosides from the holothurian Cladolabes sp.

Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, USSR Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 764–765, September–October, 1988.     

Gas phase glycosidic cleavage of oxynions from alkyl glycosides

The oxyanion [M? H]^? from several methylglycosides were generated by fast atom bombardment and their decomposition was studied by mass-analysed ion kinetic energy spectrometry. The main decomposition pathway is the loss of methanol. The hydroxylic hydrogen arises by proton transfer from the hydroxyl groups of the sugar. In the gluco-series, no anomeric effect is found. The absence of either the hydroxyl groups at C-2 or C-6 does not inhibit the glycosidic cleavage. However, the blocking of both the hydroxyl groups at C-4 and C-6, by a benzylidene group or two methyl groups, inhibit completely the glycosidic cleavage. From these results, it is proposed that the glycosidic cleavage occurs after opening the sugar ring by a vicinal attack of an oxyanion at C-6 or C-4 to the C-5 carbon atom. Then, the ionized hemi-acetals fragment into a methanolate anion and a 5,6- or 4,5-anhydrosugar which exchange another proton before their separation into charged and neutral species.     

Evaluation of solid and submerged fermentations for the production of cyclodextrin glycosyltransferase by Paenibacillus campinasensis H69-3 and characterization of crude enzyme

Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins from starch by an intramolecular transglycosylation reaction. Cyclodextrins have been shown to have a number of applications in the food, cosmetic, pharmaceutical, and chemical industries. In the current study, the production of CGTase by Paenibacillus campinasensis strain H69-3 was examined in submerged and solid-state fermentations. P. campinasensis strain H69-3 was isolated from the soil, which grows at 45°C, and is a Gramvariable bacterium. Different substrate sources such as wheat bran, soybean bran, soybean extract, cassava solid residue, cassava starch, corn starch, and other combinations were used in the enzyme production. CGTase activity was highest in submerged fermentations with the greatest production observed at 48–72 h. The physical and chemical properties of CGTase were determined from the crude enzyme produced from submerged fermentations. The optimum temperature was found to be 70–75°C, and the activity was stable at 55°C for 1 h. The enzyme displayed two optimum pH values, 5.5 and 9.0 and was found to be stable between a pH of 4.5 and 11.0.     

Synthesis of O-spiro-C-aryl glycosides using organocatalysis

An organocatalysis strategy has been developed toward the synthesis of O-spiro-C-aryl glycosides with different configurations in the sugar part. This strategy has been extended to the synthesis of the Papulacandin class of compounds.     

Aglycon switch approach toward unnatural glycosides from natural glycoside with glycosyltransferase VinC

New aglycon switch approach using glycosyltransferase VinC was explored to create unnatural glycosides from natural glycoside in one-pot reaction. This aglycon switch comprises from two reactions, where NDP-vicenisamine generated in situ from natural glycoside vicenistatin and NDP by the reverse reaction is transferred to the targeted additional aglycons to form unnatural vicenisaminides by the forward reaction.     

A new phenol compound from endophytic Phomopsis sp. DC01

The strain DC01 was isolated from the branch tissue of Daphniphyllum longeracemosum and determined to be a member of Phomopsis according to the ITS sequence analysis. The extracts from the PDA solid fermentation media of Phomopsis sp. DC01 were purified and three compounds including one new phenol compound were obtained. The new compound was identified to be (E?)-7-(2-hydroxy-4-(hydroxymethyl)phenyl)-2-methyloct-6-enoic acid (1) based on 1-D NMR, 2-D NMR and HR-ESI data.     

GNPS-Guided Discovery of Madurastatin Siderophores from the Termite-Associated Actinomadura sp. RB99**

In this study, we analyzed if Actinomadura sp. RB99 produces siderophores that that could be responsible for the antimicrobial activity observed in co-cultivation studies. Dereplication of high-resolution tandem mass spectrometry (HRMS/MS) and global natural product social molecular networking platform (GNPS) analysis of fungus-bacterium co-cultures resulted in the identification of five madurastatin derivatives (A1, A2, E1, F, and G1), of which were four new derivatives. Chemical structures were unambiguously confirmed by HR-ESI-MS, 1D and 2D NMR experiments, as well as MS/MS data and their absolute structures were elucidated based on Marfey's analysis, DP4+ probability calculation and total synthesis. Structure analysis revealed that madurastatin E1 ( 2 ) contained a rare 4-imidazolidinone cyclic moiety and madurastatin A1 ( 5 ) was characterized as a Ga³⁺-complex. The function of madurastatins as siderophores was evaluated using the fungal pathogen Cryptococcus neoformans as model organism. Based on homology models, we identified the putative NRPS-based gene cluster region of the siderophores in Actinomadura sp. RB99.     

Synthesis and mycobacterial growth inhibition activities of bivalent and monovalent arabinofuranoside containing alkyl glycosides

Arabinofuranosides constitute one of the important components of cell wall structures of mycobacteria. With this importance of arabinofuranosides in mind, alkyl glycosides bearing arabinofuranoside trisaccharides were prepared, wherein the sugars were presented either in the monovalent or bivalent forms. Following the synthesis, the monovalent and bivalent alkyl glycosides were tested for their activities in a mycobacterial growth assay. The growth of the mycobacterial strain M. smegmatis was assessed in the presence of the alkyl glycosides and it was realized that the alkyl glycosides acted as inhibitors of the mycobacterial growth. The inhibition of the growth, caused by the above alkyl glycosides, was not observed for the arabinofuranose trisaccharide alone, without the alkyl groups, and for an alkyl glycoside bearing maltose as the sugar component.     

Structures of micelles formed by synthetic alkyl glycosides with unsaturated alkyl chains

Three new alkyl glycosides with similar molecular structures (oleyl and oleoyl alkyl chains and various head groups: disaccharide, trisaccharide and disaccharide with an additional amidoethoxy spacer) were synthesized and their supramolecular structure in aqueous solution was investigated. Small angle neutron scattering, surface tension measurement and the contact preparation method were applied to get molecular structure-property relationships. Although the chemical structures differ only in small details, their CMC values, lyotropic phase behaviour, surface area per surfactant molecule in the micelle and at the liquid-air interface, and the size and shape of the micelles are very different. We have found three different types of aggregates: spherical, cylindrical and polymer-like micelles in dilute solutions.     

Synthesis of alpha-D-idoseptanosyl glycosides using an S-phenyl septanoside donor

[reaction: see text] An S-phenyl alpha-D-idoseptanoside donor was used in the selective preparation of a series of alpha-D-idoseptanosyl glycosides. Glycosylation of a methyl beta-D-glycero-D-guloseptanoside acceptor with the new donor constituted the first synthesis of a septanose disaccharide.     

Synthesis of alkyl-H-phosphinic acid alkyl esters from red phosphorus and alkyl bromides

Alkyl-H-phosphinic acid alkyl esters are synthesized in 65–71% yield via chemoselective reaction of alkyl bromides with available alkyl-H-phosphinic acids (60–65 °C, Et3N). The latter are prepared, in turn, by direct phosphorylation of alkyl bromides with red phosphorus under phase-transfer conditions.     

Synthesis of C-aryl and C-alkyl glycosides using glycosyl phosphates

[reaction: see text] Mannosyl and glucosyl phosphate donors were successfully used in constructing C-aryl linkages common to many natural products via a Lewis acid induced Fries-like rearrangement. The rearrangement was stereo- and regiospecific, yielding only one C-glycoside product. C-Alkyl glycoside carbohydrate mimetics were generated by using silicon-derived C-nucleophiles and glycosyl phosphates.     

One-step syntheses of alkyl glycosides and alkyl-substituted DNA oligomers by chemoselective glycosidations using DNA bases

The simple and practical synthesis of alkyl glycosides by novel chemoselective glycosidations using natural resources, DNA and RNA nucleosides, was realized, and the one-step synthesis of chemoselectively modified DNA oligomers using the glycosidation method was also demonstrated.     

Synthesis of degraded cyanogenic glycosides from Sambucus nigra

Two natural cyanohydrins, isolated from Sambucus nigra, have been synthesised from mandelonitrile and penta-O-acetyl-beta-galactopyranose. The synthesis confirmed the stereochemistry of the compounds, which had been assigned on biogenetic grounds.     

Synthesis of carbamate-containing cyclodextrin analogues

[formula: see text] The one-pot cyclooligomerization of a saccharide-derived p-nitrophenyl carbamate monomer was developed to generate a series of novel carbamate-containing cyclodextrin analogues. The "transcarbamoylation" occurs by initial base-induced activation to the isocyanate, followed by polycondensation/cyclization of the isocyanato alcohol. In the presence of NaH, only cyclized oligomers were observed, suggesting the importance of Na+ in promoting the efficiency of the cyclization process. The facile deprotection of the oligomers was achieved.