Search Results (12)

α-L-Rhamnosidase can specifically hydrolyze plant natural glycosides and holds significant potential for biocatalytic applications in functional foods, healthy products, and pharmaceutical industries. Herein, a novel thermophilic and acidophilic α-L-rhamnosidase TsRha from Thermotoga sp. 2812B belonging to glycoside hydrolase family 78 was identified by genome mining and comprehensively characterized by bioinformatics, computer-aided structural analysis, and biochemical characterization. TsRha possesses a domain architecture comprising one catalytic (α/α)₆-barrel domain and four β-sheet domains. TsRha displayed optimal activity at 90 °C and pH 5.0, remarkable thermostability at 80 °C, and considerable tolerance to organic solvents. TsRha exhibited broad substrate selectivity and might efficiently hydrolyze a series of natural flavonoid glycosides with various glycosidic bonds (α-1, α-1, 2, α-1, 6) from different aglycone subgroups (flavanone, flavone, flavonol, and dihydrochalcone). Moreover, it demonstrated high conversion efficiencies toward a variety of natural flavonoid diglycosides rutin, naringin, naringin dihydrochalcone, hesperidin, and troxerutin, achieving ≥99.1% conversion within 20~100 min. The excellent properties including high activity, thermophilicity, acidophilicity, good thermostability, broad substrate spectrum will make the α-L-rhamnosidase TsRha a promising biocatalyst for the efficient production of rare and high-value flavonoid glucosides with improved bioavailability and bioactivity. Full article

A novel, eco-friendly, and efficient method for constructing 2,3-disubstituted chromone skeletons from readily available water, o-hydroxyaryl enaminones (o-HPEs), and aryldiazonium salts has been developed under mild reaction conditions. This α,β-C(sp²)–H bond difunctionalization/chromone annulation reaction strategy is achieved by building two C(sp³)–O bonds and a C(sp²)-N bond, which provides a practical pathway for the preparation of 2-hydroxy-3-hydrazono-chromones in moderate to excellent yields, enabling broad substrate scope and good functional group tolerance, as well as gram-scale synthesis. This protocol offers a valuable tool for synthesizing diverse functionalized chromones with potential applications in drug discovery and industrial synthesis. Full article

Agarase and its metabolites are reported to have applications in a variety of fields, but there have been few studies of the effects of agaro-oligosaccharide hydrolysate on muscle function. In this study, we analyzed the functionality of agarase and its metabolites in bacteria isolated from seawater. A bacterium with agar-degrading activity was isolated from Shimabara, Nagasaki, Japan. Through 16S rRNA sequence alignment, it was identified as being closely related to Rheinheimera sp. WMF-1 and was provisionally named Rheinheimera sp. (HY). Crude enzymes derived from this bacterium demonstrated an ability to hydrolyze various polysaccharides, including agar, agarose, and starch, with the highest specificity observed for agarose. The optimum pH and temperature were pH 10 and 50 °C. A glycoside bond specificity analysis of enzymatic activity indicated the cleavage of the α-linkage. Next, we investigated the functional effects of agaro-oligosaccharides on C2C12 myotubes. Treatment with 10–30 kDa oligosaccharides significantly increased the hypertrophy rate, diameter, and expression of myosin heavy-chain genes in C2C12 myotubes. These results indicate that the agaro-oligosaccharides produced by the enzymes identified in this study improve muscle mass, suggesting their potential contribution to muscle function. Full article

The Sc(OTf)₃-catalyzed dearomative [5+1] annulations between readily available 3-aminophenols and O-alkyl ortho-oxybenzaldehydes were developed for synthesis of spiro[chromane-3,1′-cyclohexane]-2′,4′-dien-6′-ones. The “two-birds-with-one-stone” strategy was disclosed by the dearomatization of phenols and direct α-C(sp³)–H bond functionalization of oxygen through cascade condensation/[1,5]-hydride transfer/dearomative-cyclization process. In addition, the antifungal activity assay and derivatizations of products were conducted to further enrich the utility of the structure. Full article

2-Pyridone ligand-facilitated palladium-catalyzed direct C–H bond functionalization via the transient directing group strategy has become an attractive topic. Here, we report a Pd-catalyzed direct β-C(sp³)–H arylation reaction of tertiary aliphatic aldehydes by using an α-amino acid as a transient directing group in combination with a 2-pyridone ligand. Full article

The glycine motif is widely prevalent in bioactive peptides. Thus, the direct and precise modification of glycine derivatives has attracted significant attention over the past few decades. Among various protocols for the modification of glycine derivatives, the visible-light-driven direct α-C(sp³)–H bond functionalization of glycine derivatives has emerged as a powerful tool to achieve this objective, owing to its merits in atom economy, selectivity, reaction simplicity, and sustainability. This review summarizes the recent advancements in visible-light-driven direct α-C(sp³)–H bond functionalization of glycine derivatives. The contents of this review are organized based on the photocatalysts employed and the various reaction modes in the functionalization process. The mechanism, the challenges encountered, and future trends are also discussed, enabling readers to understand the current developmental status in this field. Full article

Dextranase, also known as glucanase, is a hydrolase enzyme that cleaves α-1,6 glycosidic bonds. In this study, a dextranase-producing strain was isolated from water samples of the Qingdao Sea and identified as Microbacterium sp. This strain was further evaluated for growth conditions, enzyme-producing conditions, enzymatic properties, and hydrolysates. Yeast extract and sodium chloride were found to be the most suitable carbon and nitrogen sources for strain growth, while sucrose and ammonium sodium were found to be suitable carbon and nitrogen sources for fermentation. The optimal pH was 7.5, with a culture temperature of 40 °C and a culture time of 48 h. Dextranase produced by strain XD05 showed good thermal stability at 40 °C by retaining more than 70% relative enzyme activity. The pH stability of the enzyme was better under a weak alkaline condition (pH 6.0–8.0). The addition of NH₄⁺ increased dextranase activity, while Co²⁺ and Mn²⁺ had slight inhibitory effects on dextranase activity. In addition, high-performance liquid chromatography showed that dextran is mainly hydrolyzed to maltoheptanose, maltohexanose, maltopentose, and maltootriose. Moreover, it can form corn porous starch. Dextranase can be used in various fields, such as food, medicine, chemical industry, cosmetics, and agriculture. Full article

The aromatic C(sp²)-H functionalization of unprotected naphthols with α-phenyl-α-diazoesters under mild conditions catalyzed by CuCl and CuCl₂ exhibits high efficiency and unique ortho-selectivity. In this study, the combination of density functional theory (DFT) calculations and experiments is employed to investigate the mechanism of C-H functionalization, which reveals the fundamental origin of the site-selectivity. It explains that CuCl-catalyzed ortho-selective C-H functionlization is due to the bimetallic carbene, which differs from the reaction catalyzed by CuCl₂ via monometallic carbene. The results demonstrate the function of favourable H-bond interactions on the site- and chemo-selectivity of reaction through stabilizing the rate-determining transition states in proton (1,3)-migration. Full article

3-Ketosteroid-Δ¹-dehydrogenases (KstDs [EC 1.3.99.4]) catalyze the Δ¹-dehydrogenation of steroids and are a class of important enzymes for steroid biotransformations. In this study, nine putative kstD genes from different origins were selected and overexpressed in Escherichia coli BL21(DE3). These recombinant enzymes catalyzed the Δ¹-desaturation of a variety of steroidal compounds. Among them, the KstD from Propionibacterium sp. (PrKstD) displayed the highest specific activity and broad substrate spectrum. The detailed catalytic characterization of PrKstD showed that it can convert a wide range of 3-ketosteroid compounds with diverse substituents, ranging from substituents at the C9, C10, C11 and C17 position through substrates without C4-C5 double bond, to previously inactive C6-substituted ones such as 11β,17-dihydroxy-6α-methyl-pregn-4-ene-3,20-dione. Reaction conditions were optimized for the biotransformation of hydrocortisone in terms of pH, temperature, co-solvent and electron acceptor. By using 50 g/L wet resting E. coli cells harboring PrKstD enzyme, the conversion of hydrocortisone was about 92.5% within 6 h at the substrate concentration of 80 g/L, much higher than the previously reported results, demonstrating the application potential of this new KstD. Full article

This study evaluated the ability of a dextranase from a marine bacterium Catenovulum sp. (Cadex) to impede formation of Streptococcus mutans biofilms, a primary pathogen of dental caries, one of the most common human infectious diseases. Cadex was purified 29.6-fold and had a specific activity of 2309 U/mg protein and molecular weight of 75 kDa. Cadex showed maximum activity at pH 8.0 and 40 °C and was stable at temperatures under 30 °C and at pH ranging from 5.0 to 11.0. A metal ion and chemical dependency study showed that Mn²⁺ and Sr²⁺ exerted positive effects on Cadex, whereas Cu²⁺, Fe³⁺, Zn²⁺, Cd²⁺, Ni²⁺, and Co²⁺ functioned as inhibitors. Several teeth rinsing product reagents, including carboxybenzene, ethanol, sodium fluoride, and xylitol were found to have no effects on Cadex activity. A substrate specificity study showed that Cadex specifically cleaved the α-1,6 glycosidic bond. Thin layer chromatogram and high-performance liquid chromatography indicated that the main hydrolysis products were isomaltoogligosaccharides. Crystal violet staining and scanning electron microscopy showed that Cadex impeded the formation of S. mutans biofilm to some extent. In conclusion, Cadex from a marine bacterium was shown to be an alkaline and cold-adapted endo-type dextranase suitable for development of a novel marine agent for the treatment of dental caries. Full article

Lithium, sodium, potassium, rubidium and caesium salts of 5-O-caffeoylquinic acid (chlorogenic acid, 5-CQA) were synthesized and described by FT-IR (infrared spectroscopy), FT-Raman (Raman spectroscopy), UV (UV absorption spectroscopy), ¹H (400.15 MHz), ¹³C (100.63 MHz) NMR (nuclear magnetic resonance spectroscopy). The quantum–chemical calculations at the B3LYP/6-311++G** level were done in order to obtain the optimal structures, IR spectra, NBO (natural bond orbital) atomic charges, HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) orbitals and chemical reactivity parameters for 5-CQA and Li, Na and K 5-CQAs (chlorogenates). The DPPH (α, α-diphenyl-β-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assays were used for the preliminary estimation of the antioxidant properties of alkali metal chlorogenates and chlorogenic acid. In the DPPH assay the EC₅₀ parameter were equal to 7.39 μM for 5-CQA and was in the range of 4.50–5.89 μM for salts. The FRAP values for two different concentrations (5 and 2.5 μM) of the studied compounds were respectively 114.22 and 72.53 μM Fe²⁺ for 5-CQA, whereas for salts they were 106.92–141.13 and 78.93–132.00 μM Fe²⁺. The 5-CQA and its alkali metal salts possess higher antioxidant properties than commonly applied antioxidants (BHA, BHT, l-ascorbic acid). The pro-oxidant action of these compounds on trolox oxidation was studied in the range of their concentration 0.05–0.35 μM. The lipophilicity (logk_w) of chlorogenates and chlorogenic acid was determined by RP-HPLC (reverse phase—high performance liquid chromatography) using five different columns (C8, PHE (phenyl), CN (cyano), C18, IAM (immobilized artificial membrane)). The compounds were screened for their in vitro antibacterial activity against E. coli, Bacillus sp., Staphylococcus sp., Streptococcus pyogenes and antifungal activity against Candida sp. The 5-CQA possessed lower antibacterial (minimal inhibitory concentration, MIC = 7.06 mM) and antifungal (MIC = 14.11 mM) properties than its alkali metal salts (MIC values: 6.46–2.63 mM and 12.91–5.27mM, respectively). The synthesized chlorogenates possessed better antioxidant, lipophilic, antimicrobial as well as lower pro-oxidant properties than the ligand alone. Moreover, a systematic change of the activity of alkali metal salts along the series Li→Cs suggests that there are correlations between the studied biological properties. The type of metal cation in the carboxylate group of chlorogenate is crucial for the activity of studied compounds. Full article

Lectin from the seeds of Dioclea lasiophylla (DlyL) was purified in a single step by affinity chromatography on a Sephadex^® G-50 column. DlyL strongly agglutinated rabbit erythrocytes and was inhibited by monosaccharides (_D-mannose and α-methyl-D-mannoside) and glycoproteins (ovalbumin and fetuin). Similar to other Diocleinae lectins, DlyL has three chains, α, β and γ, with mass of 25,569 ± 2, 12,998 ± 1 and 12,588 ± 1 Da, respectively, and has no disulfide bonds. The hemagglutinating activity of DlyL was optimal in pH 8.0, stable at a temperature of 70 °C and decreased in EDTA solution, indicating that lectin activity is dependent on divalent metals. DlyL exhibited low toxicity on Artemia sp. nauplii, but this effect was dependent on the concentration of lectin in solution. DlyL immobilized on cyanogen bromide-activated Sepharose^® 4B bound 0.917 mg of ovalbumin per cycle, showing the ability to become a tool for glycoproteomics studies. Full article