Synthesis of α(1→4)-linked non-natural mannoglucans by α-glucan phosphorylase-catalyzed enzymatic copolymerization

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Chemoenzymatic synthesis of carboxylate-terminated maltooligosaccharides and their use for cross-linking of chitin

In this paper, we report chemoenzymatic synthesis of maltooligosaccharides having carboxylate groups at both ends (carboxylate-terminated maltooligosaccharides, GlcA-Glc_n-GlcCOONa). The products were further used as cross-linker for water-soluble chitin (WSCh) to obtain network chitins. The synthesis of GlcA-Glc_n-GlcCOONa was achieved by thermostable phosphorylase-catalyzed enzymatic α-glucuronylation using α-d-glucuronic acid 1-phosphate with a carboxylated maltooligosaccharide, which was prepared by chemical oxidation at the reducing end of maltoheptaose with sodium hypoiodite. The structures of GlcA-Glc_n-GlcCOONa were evaluated by ¹H NMR and MALDI-TOF mass spectra. The obtained GlcA-Glc_n-GlcCOONa were used as cross-linker for WSCh by condensation in the presence of condensing agent. The reaction mixtures totally turned into hydrogel form in most cases. Morphologies of lyophilized samples (cryogels) from the hydrogels were evaluated by SEM measurement. The hydrogels could be converted into films by pressing. Furthermore, mechanical properties of the hydrogels and films were investigated by compression and tensile tests, respectively.

Thermostable α-Glucan Phosphorylase-Catalyzed Enzymatic Copolymerization to Produce Partially 2-Deoxygenated Amyloses

α-Glucan phosphorylase catalyzes the enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) monomers from a maltooligosaccharide primer to produce α(1→4)-glucan—i.e., amylose. In this study, by exploiting the weak specificity for the substrate recognition of a thermostable α-glucan phosphorylase (from Aquifex aeolicus VF5), we investigated the enzymatic copolymerization of 2-deoxy-α-d-glucose 1-phosphate (dGlc-1-P), which was produced in situ from d-glucal, with Glc-1-P to obtain non-natural heteropolysaccharides composed of α(1→4)-linked dGlc/Glc units—i.e., partially 2-deoxygenated amylose. The reactions were carried out at different monomer feed ratios using a maltotriose primer at 40 °C for 24 h. The products were precipitated from the reaction medium, isolated by centrifugation, and subjected to 1H NMR spectroscopic and powder X-ray diffraction measurements to evaluate their chemical and crystalline structures, respectively. Owing to its amorphous nature, the partially 2-deoxygenated amylose with adapted unit ratios formed a film when subjected to a casting method.

Enzymatic synthesis of functional amylosic materials and amylose analog polysaccharides

Because polysaccharides have very complicated chemical structures constructed by a great diversity of monosaccharide residues and glycosidic linkages, enzymatic approaches have been identified as powerful tools to precisely synthesize polysaccharides as the reactions progress in highly controlled regio- and stereoarrangements. α-Glucan phosphorylase (GP) is one of the enzymes that have acted as catalysts for the practical production of well-defined polysaccharides. GP can catalyze enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) as a monomer from a maltooligosaccharide primer to produce a pure amylose with well-defined structure via the formation of α(1→4)-glycosidic linkages. Here, the author presents methods which achieve the enzymatic synthesis of functional amylosic materials and amylose analog polysaccharides by GP-catalyzed enzymatic polymerization approaches. As the polymerization progresses at the non-reducing end of the primer, it can be conducted using polymeric primers that are modified at the reducing end and covalently attached on suitable polymeric chains. By using such polymeric primers, various amylose-grafted functional materials can be enzymatically synthesized. For example, the detailed protocol for the synthesis of amylose-grafted poly(γ-glutamic acid) is described. GP shows loose specificity for the recognition of substrates, which allows to recognize some monosaccharide 1-phosphates as analog substrates of Glc-1-P. Representatively, the experimental procedure of the GP-catalyzed enzymatic polymerization of α-d-glucosamine 1-phosphate as the analog substrate is presented to synthesize an α(1→4)-linked glucosamine polymer, that is called amylosamine. By means of a similar approach catalyzed by GP, several amylose analog polysaccharides have been obtained.

α-Glucan Phosphorylase-Catalyzed Enzymatic Reactions Using Analog Substrates to Synthesize Non-Natural Oligo- and Polysaccharides

As natural oligo- and polysaccharides are important biomass resources and exhibit vital biological functions, non-natural oligo- and polysaccharides with a well-defined structure can be expected to act as new functional materials with specific natures and properties. α-Glucan phosphorylase (GP) is one of the enzymes that have been used as catalysts for practical synthesis of oligo- and polysaccharides. By means of weak specificity for the recognition of substrates by GP, non-natural oligo- and polysaccharides has precisely been synthesized. GP-catalyzed enzymatic glycosylations using several analog substrates as glycosyl donors have been carried out to produce oligosaccharides having different monosaccharide residues at the non-reducing end. Glycogen, a highly branched natural polysaccharide, has been used as the polymeric glycosyl acceptor and primer for the GP-catalyzed glycosylation and polymerization to obtain glycogen-based non-natural polysaccharide materials. Under the conditions of removal of inorganic phosphate, thermostable GP-catalyzed enzymatic polymerization of analog monomers occurred to give amylose analog polysaccharides.

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.