Immobilization of the Highly Active UDP-Glucose Pyrophosphorylase From Thermocrispum agreste Provides a Highly Efficient Biocatalyst for the Production of UDP-Glucose

Combining an Enhanced Polyphosphate Kinase-Driven UDP-Glucose Regeneration System with the Screening of Key Glycosyltransferases for Efficient In Vitro Synthesis of Nucleoside Disaccharides

Nucleoside disaccharides are essential glycosides that naturally occur in specific living organisms. This study developed an enhanced UDP-glucose regeneration system to facilitate the in vitro multienzyme synthesis of nucleoside disaccharides by integrating it with nucleoside-specific glycosyltransferases. The system utilizes maltodextrin and polyphosphate as cost-effective substrates for UDP-glucose supply, catalyzed by α-glucan phosphorylase (αGP) and UDP-glucose pyrophosphorylase (UGP). To address the low activity of known polyphosphate kinases (PPKs) in the UDP phosphorylation reaction, a sequence-driven screening identified RhPPK with high activity against UDP (>1000 U/mg). Computational design further led to the creation of a double mutant with a 2566-fold increase in thermostability at 50 °C. The enhanced UDP-glucose regeneration system increased the production rate of nucleoside disaccharide synthesis by 25-fold. In addition, our UDP-glucose regeneration system is expected to be applied to other glycosyl transfer reactions.

Engineering a Robust UDP-Glucose Pyrophosphorylase for Enhanced Biocatalytic Synthesis via ProteinMPNN and Ancestral Sequence Reconstruction

UDP-glucose is a key metabolite in carbohydrate metabolism and plays a vital role in glycosyl transfer reactions. Its significance spans across the food and agricultural industries. This study focuses on UDP-glucose synthesis via multienzyme catalysis using dextrin, incorporating UTP production and ATP regeneration modules to reduce costs. To address thermal stability limitations of the key UDP-glucose pyrophosphorylase (UGP), a deep learning-based protein sequence design approach and ancestral sequence reconstruction are employed to engineer a thermally stable UGP variant. The engineered UGP variant is significantly 500-fold more thermally stable at 60 °C and has a half-life of 49.8 h compared to the wild-type enzyme. MD simulations and umbrella sampling calculations provide insights into the mechanism behind the enhanced thermal stability. Experimental validation demonstrates that the engineered UGP variant can produce 52.6 mM UDP-glucose within 6 h in an in vitro cascade reaction. This study offers practical insights for efficient UDP-glucose synthesis methods.

Biocatalytic Approaches to Building Blocks for Enzymatic and Chemical Glycan Synthesis

While the field of biocatalysis has bloomed over the past 20-30 years, advances in the understanding and improvement of carbohydrate-active enzymes, in particular, the sugar nucleotides involved in glycan building block biosynthesis, have progressed relatively more slowly. This perspective highlights the need for further insight into substrate promiscuity and the use of biocatalysis fundamentals (rational design, directed evolution, immobilization) to expand substrate scopes toward such carbohydrate building block syntheses and/or to improve enzyme stability, kinetics, or turnover. Further, it explores the growing premise of using biocatalysis to provide simple, cost-effective access to stereochemically defined carbohydrate materials, which can undergo late-stage chemical functionalization or automated glycan synthesis/polymerization.

Co-Immobilization of D-Amino Acid Oxidase, Catalase, and Transketolase for One-Pot, Two-Step Synthesis of L-Erythrulose

Here, we present an immobilized enzyme cascade in a basket-type reactor allowing a one-pot, two-step enzymatic synthesis of L-erythrulose from D-serine and glycolaldehyde. Three enzymes, D-amino acid oxidase from Rhodotorula gracilis (DAAORg), catalase from bovine liver (CAT), and transketolase from Geobacillus stearothermophilus (TKgst) were covalently immobilized on silica monolithic pellets, characterized by an open structure of interconnected macropores and a specific surface area of up to 300 m2/g. Three strategies were considered: (i) separate immobilization of enzymes on silica supports ([DAAO][CAT][TK]), (ii) co-immobilization of two of the three enzymes followed by the third ([DAAO+CAT][TK]), and (iii) co-immobilization of all three enzymes ([DAAO+CAT+TK]). The highest L-erythrulose concentrations were observed for the co-immobilization protocols (ii) and (iii) (30.7 mM and 29.1 mM, respectively). The reusability study showed that the best combination was [DAAO + CAT][TK], which led to the same level of L-erythrulose formation after two reuse cycles. The described process paves the way for the effective synthesis of a wide range of α-hydroxyketones from D-serine and suitable aldehydes.

Enzyme cascades for the synthesis of nucleotide sugars: Updates to recent production strategies

Nucleotide sugars play an elementary role in nature as building blocks of glycans, polysaccharides, and glycoconjugates used in the pharmaceutical, cosmetics, and food industries. As substrates of Leloir-glycosyltransferases, nucleotide sugars are essential for chemoenzymatic in vitro syntheses. However, high costs and the limited availability of nucleotide sugars prevent applications of biocatalytic cascades on a large industrial scale. Therefore, the focus is increasingly on nucleotide sugar synthesis strategies to make significant application processes feasible. The chemical synthesis of nucleotide sugars and their derivatives is well established, but the yields of these processes are usually low. Enzyme catalysis offers a suitable alternative here, and in the last 30 years, many synthesis routes for nucleotide sugars have been discovered and used for production. However, many of the published procedures shy away from assessing the practicability of their processes. With this review, we give an insight into the development of the (chemo)enzymatic nucleotide sugar synthesis pathways of the last years and present an assessment of critical process parameters such as total turnover number (TTN), space-time yield (STY), and enzyme loading.

Efficient Synthesis of cis-4-Propylcyclohexanol Using a Mutant Alcohol Dehydrogenase Coupled with Glucose Dehydrogenase

cis-4-Propylcyclohexanol is an important intermediate for synthesizing trans-2-(4-propylcyclohexyl)-1,3-propanediol, which is widely used in the manufacture of liquid crystal displays. In this study, cis-4-propylcyclohexanol was prepared using a mutant alcohol dehydrogenase from Lactobacillus kefir (LK-TADH, A94T/F147L/L199H/A202L) coupled with glucose dehydrogenase. Using the optimal catalytic conditions, 125 g/L (250 g) of 4-propylcyclohexanone was completely transformed after 5 h, and 225.8 g of cis-4-propylcyclohexanol (cis/trans ratio of 99.5:0.5) was obtained through extraction and rotary evaporation at a yield of 90.32%. This study reports a potential method for the green production of cis-4-propylcyclohexanol as the key intermediate of trans-2-(4-propylcyclohexyl)-1,3-propanediol at an industrial level.