A convenient gram-scale synthesis of uridine diphospho(13C6)glucose

Highly Efficient Production of UDP-Glucose from Sucrose via the Semirational Engineering of Sucrose Synthase and a Cascade Route Design

Nucleotide sugars are essential precursors for carbohydrate synthesis but are in scarce supply. Uridine diphosphate (UDP)-glucose is a core building block in nucleotide sugar preparation, making its efficient synthesis critical. Here, a process for producing valuable UDP-glucose and functional mannose from sucrose was established and improved via a semirational sucrose synthase (SuSy) design and the accurate D-mannose isomerase (MIase) cascade. Engineered SuSy exhibited enzyme activity 2.2-fold greater than that of the WT. The structural analysis identified a latch-hinge combination as the hotspot for enhancing enzyme activity. Coupling MIase, process optimization, and reaction kinetic analysis revealed that MIase addition during the high-speed UDP-glucose synthesis phase distinctly accelerated the entire process. The simultaneous triggering of enzyme modules halved the reaction time and significantly increased the UDP-glucose yield. A maximum UDP-glucose yield of 83%, space-time yield of 70 g/L/h, and mannose yield of 32% were achieved. This novel and efficient strategy for sucrose value-added exploitation has industrial promise.

Engineering the Thermostability of Sucrose Synthase by Reshaping the Subunit Interaction Contributes to Efficient UDP-Glucose Production

The restricted availability of UDP-glucose, an essential precursor that targets oligo/polysaccharide and glycoside synthesis, makes its practical application difficult. Sucrose synthase (Susy), which catalyzes one-step UDP-glucose synthesis, is a promising candidate. However, due to poor thermostability of Susy, mesophilic conditions are required for synthesis, which slow down the process, limit productivity, and prevent scaled and efficient UDP-glucose preparation. Here, we obtained an engineered thermostable Susy (mutant M4) from Nitrosospira multiformis through automated prediction and greedy accumulation of beneficial mutations. The mutant improved the T_1/2 value at 55 °C by 27-fold, resulting in UDP-glucose synthesis at 37 g/L/h of space-time yield that met industrial biotransformation standards. Furthermore, global interaction between mutant M4 subunits was reconstructed by newly formed interfaces according to molecular dynamics simulations, with residue Trp162 playing an important role in strengthening the interface interaction. This work enabled effective, time-saving UDP-glucose production and paved the way for rational thermostability engineering of oligomeric enzymes.

Synthesis and Antibacterial Properties of Oligomeric Dehydrogenation Polymer from Lignin Precursors

The lignin precursors of coniferin and syringin were synthesised, and guaiacyl-type and guaiacyl-syringyl-type oligomeric lignin dehydrogenation polymers (DHP and DHP-GS) were prepared with the bulk method. The carbon-13 nuclear magnetic resonance spectroscopy showed that both DHP-G and DHP-GS contained β-O-4, β-5, β-β, β-1, and 5-5 substructures. Extraction with petroleum ether, ether, ethanol, and acetone resulted in four fractions for each of DHP-G (C11-C14) and DHP-GS (C21-C24). The antibacterial experiments showed that the fractions with lower molecular weight had relatively strong antibacterial activity. The ether-soluble fractions (C12 of DHP-G and C22 of DHP-GS) had strong antibacterial activities against E. coli and S. aureus. The C12 and C22 fractions were further separated by preparative chromatography, and 10 bioactive compounds (G1-G5 and GS1-GS5) were obtained. The overall antibacterial activities of these 10 compounds was stronger against E. coli than S. aureus. Compounds G1, G2, G3, and GS1, which had the most significant antibacterial activities, contained β-5 substructures. Of these, G1 had the best antibacterial activity. Its inhibition zone diameter was 19.81 ± 0.82 mm, and the minimum inhibition concentration was 56.3 ± 6.20 μg/mL. Atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) showed that the antibacterial activity of G1 was attributable to a phenylcoumarin dimer, while the introduction of syringyl units reduced antibacterial activity.

One-Step Synthesis of Sugar Nucleotides

The chemical synthesis of sugar nucleotides requires a multistep procedure to ensure a selective reaction. Herein, sugar nucleotides were synthesized in one step using 2-chloro-1,3-dimethylimidazolinium chloride as the condensation reagent. The products were obtained in yields of 12-30%, and the yields were increased to 35-47% by the addition of a tuning reagent. NMR identification of the sugar nucleotides showed that mainly 1,2-trans-glycosides were present. The reported method represents a one-step route to sugar nucleotides from commercially available materials.

Synthesis of selected unnatural sugar nucleotides for biotechnological applications

Sugar nucleotides are the principal building blocks for the synthesis of most complex carbohydrates and are crucial intermediates in carbohydrate metabolism. Uridine diphosphate (UDP) monosaccharides are among the most common sugar nucleotide donors and are transferred to glycosyl acceptors by glycosyltransferases or synthases in glycan biosynthetic pathways. These natural nucleotide donors have great biological importance, however, the synthesis and application of unnatural sugar nucleotides that are not available from in vivo biosynthesis are not well explored. In this review, we summarize the progress in the preparation of unnatural sugar nucleotides, in particular, the widely studied UDP-GlcNAc/GalNAc analogs. We focus on the "two-block" synthetic pathway that is initiated from monosaccharides, in which the first block is the synthesis of sugar-1-phosphate and the second block is the diphosphate bond formation. The biotechnological applications of these unnatural sugar nucleotides showing their physiological and pharmacological potential are discussed.

Efficient Synthesis of UDP-Furanoses via 4,5-Dicyanoimidazole(DCI)-Promoted Coupling of Furanosyl-1-Phosphates with Uridine Phosphoropiperidate

A P(V)-N activation method based on nucleoside phosphoropiperidate/DCI system has been developed for improved synthesis of diverse UDP-furanoses. The reaction conditions including temperature, amount of activator, and reaction time were optimized to alleviate the degradation of UDP-furanoses to cyclic phosphates. In addition, an efficient and facile phosphoramidite route was employed for the preparation of furanosyl-1-phosphates.

Synthesis of 4-Azido-N-acetylhexosamine Uridine Diphosphate Donors: Clickable Glycosaminoglycans

Unnatural chemically modified nucleotide sugars UDP-4-N3-GlcNAc and UDP-4-N3-GalNAc were chemically synthesized for the first time. These unnatural UDP sugar products were then tested for incorporation into hyaluronan, heparosan, or chondroitin using polysaccharide synthases. UDP-4-N3-GlcNAc served as a chain termination substrate for hyaluronan or heparosan synthases; the resulting 4-N3-GlcNAc-terminated hyaluronan and heparosan were then successfully conjugated with Alexa Fluor 488 DIBO alkyne, demonstrating that this approach is generally applicable for labeling and detection of suitable glycosaminoglycans.

Conformational Analysis of a High-Mannose-Type Oligosaccharide Displaying Glucosyl Determinant Recognised by Molecular Chaperones Using NMR-Validated Molecular Dynamics Simulation

Exploration of the conformational spaces of flexible oligosaccharides is essential to gain deeper insights into their functional mechanisms. Here we characterised dynamic conformation of a high-mannose-type dodecasaccharide with a terminal glucose residue, a critical determinant recognised by molecular chaperones. The dodecasaccharide was prepared by our developed chemoenzymatic technique, which uses ¹³ C labelling and lanthanide tagging to detect conformation-dependent paramagnetic effects by NMR spectroscopy. The NMR-validated molecular dynamics simulation produced the dynamic conformational ensemble of the dodecasaccharide. This determined its spatial distribution as well as the glycosidic linkage conformation of the terminal glucose determinant. Moreover, comparison of our results with previously reported crystallographic data indicates that the chaperone binding to its target oligosaccharides involves an induced-fit mechanism.

Promiscuous activity of ER glucosidase II discovered through donor specificity analysis of UGGT

In glycoprotein quality control system in the endoplasmic reticulum (ER), UGGT (UDP-glucose:glycoprotein glucosyltransferase) and glucosidase II (G-II) play key roles. UGGT serves as a glycoprotein folding sensor by virtue of its unique specificity to glucosylate glycoproteins at incompletely folded stage. By using various UDP-Glc analogues, we first analyzed donor specificity of UGGT, which was proven to be rather narrow. However, marginal activity was observed with UDP-galactose and UDP-glucuronic acid as well as with 3-, 4- and 6-deoxy glucose analogues to give corresponding transfer products. Intriguingly, G-II smoothly converted all of them back to Man(9)GlcNAc(2), providing an indication that G-II has a promiscuous activity as a broad specificity hexosidase.

Lipophilic sugar nucleotide synthesis by structure-based design of nucleotidylyltransferase substrates

Structure-based design of alkyl sugar-1-phosphates provides an efficient nucleotidylyltransferase-catalyzed synthesis of a series of new lipophilic sugar nucleotides possessing long or branched alkyl chains, thereby demonstrating the utility of nucleotidylyltransferases to catalyze the synthesis of sugar nucleotides with potential applications in lipopolysaccharide and lipoglycopeptide biosynthesis.

Stereoselective chemical synthesis of sugar nucleotides via direct displacement of acylated glycosyl bromides

[structure: see text]. The use of Leloir glycosyltransferases to prepare biologically relevant oligosaccharides and glycoconjugates requires access to sugar nucleoside diphosphates, which are notoriously difficult to efficiently synthesize and purify. We report a novel stereoselective route to UDP- and GDP-alpha-D-mannose as well as UDP- and GDP-beta-L-fucose via direct displacement of acylated glycosyl bromides with nucleoside 5'-diphosphates.