Facile synthesis of glucose-1-phosphate from starch by Thermus caldophilus GK24 α-glucan phosphorylase

The Power of Biocatalysts for Highly Selective and Efficient Phosphorylation Reactions

Reactions involving the transfer of phosphorus-containing groups are of key importance for maintaining life, from biological cells, tissues and organs to plants, animals, humans, ecosystems and the whole planet earth. The sustainable utilization of the nonrenewable element phosphorus is of key importance for a balanced phosphorus cycle. Significant advances have been achieved in highly selective and efficient biocatalytic phosphorylation reactions, fundamental and applied aspects of phosphorylation biocatalysts, novel phosphorylation biocatalysts, discovery methodologies and tools, analytical and synthetic applications, useful phosphoryl donors and systems for their regeneration, reaction engineering, product recovery and purification. Biocatalytic phosphorylation reactions with complete conversion therefore provide an excellent reaction platform for valuable analytical and synthetic applications.

Dictyoglomus turgidum DSM 6724 α-Glucan Phosphorylase: Characterization and Its Application in Multi-enzyme Cascade Reaction for D-Tagatose Production

Phosphorylase is a type of enzyme-producing sugar phosphates through the reversible phosphorolysis reactions of glycosides, which makes it an important starting enzyme in multi-enzyme systems for rare sugar biomanufacturing. To investigate its application in D-tagatose biosynthesis from maltodextrin using in vitro multi-enzyme cascade biosystem, the α-glucan phosphorylase (αGP; EC 2.4.1.1) from the thermophile D. turgidum DSM 6724 was prepared and characterized. It exhibited the specific activity of 30.28 U/mg at its optimal temperature of 70 °C. Thermostability results revealed that DituαGP could maintain more than 25% of initial activity for 4 h, even at 90 °C. The highest activity was observed at pH 5.5, and most divalent metal ions deactivated the enzyme. DituαGP exhibited great application potential in the multi-enzyme system that about 3.919 g/L of D-tagatose was produced from 150 g/L of maltodextrin within 36 h. DituαGP has played an important role in this biosystem and will also be applied in the synthesis of other rare sugars from maltodextrin.

Thermostable alpha-glucan phosphorylases: characteristics and industrial applications

α-Glucan phosphorylases (α-GPs) catalyze the reversible phosphorolysis of α-1,4-linked polysaccharides such as glycogen, starch, and maltodextrins, therefore playing a central role in the usage of storage polysaccharides. The discovery of these enzymes and their role in the course of catalytic conversion of glycogen was rewarded with the Nobel Prize in Physiology or Medicine in 1947. Nowadays, however, thermostable representatives attract special attention due to their vast potential in the enzymatic production of diverse carbohydrates and derivatives such as (functional) oligo- and (non-natural) polysaccharides, artificial starch, glycosides, and nucleotide sugars. One of the most recently explored utilizations of α-GPs is their role in the multi-enzymatic process of energy production stored in carbohydrate biobatteries. Regardless of their use, thermostable α-GPs offer significant advantages and facilitated bioprocess design due to their high operational temperatures. Here, we present an overview and comparison of up-to-date characterized thermostable α-GPs with a special focus on their reported biotechnological applications.

One-Pot Biosynthesis of High-Concentration α-Glucose 1-Phosphate from Starch by Sequential Addition of Three Hyperthermophilic Enzymes

α-Glucose 1-phosphate (G1P) is synthesized from 5% (w/v) corn starch and 1 M phosphate mediated by α-glucan phosphorylase (αGP) from the thermophilic bacterium Thermotoga maritima at pH 7.2 and 70 °C. To increase G1P yield from corn starch containing branched amylopectin, a hyper-thermostable isoamylase from Sulfolobus tokodaii was added for simultaneous starch gelatinization and starch-debranching hydrolysis at 85 °C and pH 5.5 before αGP use. The pretreatment of isoamylase increased G1P titer from 120 mM to 170 mM. To increase maltose and maltotriose utilization, the third thermostable enzyme, 4-glucanotransferase (4GT) from Thermococcus litoralis, was added during the late stage of G1P biotransformation, further increasing G1P titer to 200 mM. This titer is the highest G1P level obtained on starch or its derived products (maltodextrin and soluble starch). This study suggests that in vitro multienzyme biotransformation has an advantage of great engineering flexibility in terms of space and time compared with microbial fermentation.

Enzymatic production of β-D-glucose-1-phosphate from trehalose

β-D-Glucose-1-phosphate (βGlc1P) is an efficient glucosyl donor for both enzymatic and chemical glycosylation reactions but is currently very costly and not available in large amounts. This article provides an efficient production method of βGlc1P from trehalose and phosphate using the thermostable trehalose phosphorylase from Thermoanaerobacter brockii. At the process temperature of 60 °C, Escherichia coli expression host cells are lysed and cell treatment prior to the reaction is, therefore, not required. In this way, the theoretical maximum yield of 26% could be easily achieved. Two different purification strategies have been compared, anion exchange chromatography or carbohydrate removal by treatment with trehalase and yeast, followed by chemical phosphate precipitation. In a next step, βGlc1P was precipitated with ethanol but this did not induce crystallization, in contrast to what is observed with other glycosylphosphates. After conversion of the product to its cyclohexylammonium salt, however, crystals could be readily obtained. Although both purification methods were quantitative (>99% recovery), a large amount of product (50%) was lost during crystallization. Nevertheless, a production process for crystalline βGlc1P is now available from the cheap substrates trehalose and inorganic phosphate.

Efficient biosynthesis of uridine diphosphate glucose from maltodextrin by multiple enzymes immobilized on magnetic nanoparticles

Uridine diphosphate glucose (UDP-Glc) serves as a glucosyl donor in many enzymatic glycosylation processes.This paper describes a multiple enzyme, one-pot, biocatalytic system for the synthesis of UDP-Glc from low cost raw materials: maltodextrin and uridine triphosphate. Three enzymes needed for the synthesis of UDP-Glc (maltodextrin phosphorylase, glucose-1-phosphate thymidylytransferase, and pyrophosphatase)were expressed in Escherichia coli and then immobilized individually on aminofunctionalized magnetic nanoparticles. The conditions for biocatalysis were optimized and the immobilized multiple-enzyme biocatalyst could be easily recovered and reused up to five times in repeated syntheses of UDP-Glc. After a simple purification, approximately 630 mg of crystallized UDP-Glc was obtained from 1 l of reaction mixture, for a moderate yield of around 50% (UTP conversion) at very low cost.

Physiological aggregation of maltodextrin phosphorylase from Pyrococcus furiosus and its application in a process of batch starch degradation to alpha-D-glucose-1-phosphate

Maltodextrin phosphorylase from Pyrococcus furiosus (PF1535) was fused with the cellulose-binding domain of Clostridium cellulovorans serving as an aggregation module. After molecular cloning of the corresponding gene fusion construct and controlled expression in Escherichia coli BL21, 83% of total maltodextrin phosphorylase activity (0.24 U/mg of dry cell weight) was displayed in active inclusion bodies. These active inclusion bodies were easily isolated by nonionic detergent treatment and directly used for maltodextrin conversion to alpha-D-glucose-1-phosphate in a repetitive batch mode. Only 10% of enzyme activity was lost after ten conversion cycles at optimum conditions.