Enzymatic synthesis of sialyl Lex and derivatives based on a recombinant fucosyltransferase

Synthesis of an Fmoc-threonine bearing core-2 glycan: a building block for PSGL-1 via Fmoc-assisted solid-phase peptide synthesis

Selectins (L, E, and P) are vascular endothelial molecules that play an important role in the recruitment of leukocytes to inflamed tissue. In this regard, P-Selectin glycoprotein-1 (PSGL-1) has been identified as a ligand for P-Selectin. PSGL-1 binds to P-Selectin through the interaction of core-2 O-glycan expressing sialyl Lewis(x) oligosaccharide and the three tyrosine sulfate residues. Herein, we report the synthesis of threonine-linked core-2 O-glycan as an amino acid building block for the synthesis of PSGL-1. This building block was further incorporated in the Fmoc-assisted solid-phase peptide synthesis to provide a portion of the PSGL-1 glycopeptide.

Multi-enzyme one-pot strategy for the synthesis of sialyl Lewis X-containing PSGL-1 glycopeptide

An enzymatic one-pot three-step glycosylation strategy was developed for the synthesis of sLex moiety of truncated PSGL-1 glycopeptide with and without sulfation. The method provided an efficient way to afford complex glycopeptides in a semi-preparative scale without further complicated and time-consuming purification process in each glycosylation step.

Carbohydrate mimetics-based glycosyltransferase inhibitors

The search for carbohydrate mimetics-based glycosyltransferase inhibitors is a dynamic field that emerged 10 years ago. This review presents a description of the different types of glycosyltransferase inhibitors containing a carbohydrate mimetic (primarily an iminosugar, a carbasugar or a C-glycoside) and data on their biological activity whenever such data are available. The purpose of this account is to foster a synergy between the two expanding research areas of glycomimetics and glycosyltransferases.

Substrate specificity of fucosyl transferase III: An efficient synthesis of sialyl Lewisx-, sialyl Lewisa-derivatives and mimetics thereof

Fucosyl transferase III (FucT III) has previously been characterized as the most general enzyme of the FucT family, as judged from its ability to catalyze the transfer of fucose to both Galβ(1-3)GlcNAc and Galβ(1-4)GlcNAc. In order to explore the synthetic potential of FucT III for the enzymatic synthesis of sialyl Lewisx and sialyl Lewisa derivatives, its substrate specificity has been probed using a number of natural substrate mimetics. A remarkable range of acceptor substrates was found when N-acetyl glucosamine was replaced by D-glucal, (R,R)-1,2-cyclohexanediol and (R,R)-butan-2,3-diol. Although the reaction rates were low compared to the reaction with the natural substrates, they proved to be sufficient for the synthesis of preparative amounts.Key words: fucosyl transferase III, sialyl Lewisa, sialyl Lewisx, carbohydrate mimetics.

Utilization of glycosyltransferases to change oligosaccharide structures

Carbohydrates on cell surfaces are important biomolecules in various biological recognition processes. Elucidation of the biological roles of complex oligosaccharides necessitates an efficient methodology to synthesize these compounds and their analogs. Enzymatic synthesis renders itself to be useful in the construction of an oligosaccharide structure owing to its mild reaction condition, high regio- and stereoselectivity. This review article focuses on the recent progress in oligosaccharide syntheses catalyzed by glycosyltransferases, namely sialyltransferase, galactosyltransferase, fucosyltransferase, and N-acetylglucosaminyltransferase. A survey of the latest patent and literature related to this field is also included.

Glycobiotechnology: enzymes for the synthesis of nucleotide sugars

Complex carbohydrates, as constituting part of glycoconjugates such as glycoproteins, glycolipids, hormones, antibiotics and other secondary metabolites, play an active role in inter- and intracellular communication. The aim of "glycobiotechnology" as an upcoming interdisciplinary research field is to develop highly efficient synthesis strategies, including in vivo and in vitro approaches, in order to bring such complex molecules into analytical and therapeutic studies. The enzymatic synthesis of glycosidic bonds by Leloir-glycosyltransferases is an efficient strategy for obtaining saccharides with absolute stereo- and regioselectivity in high yields and under mild conditions. There are, however, two obstacles hindering the realization of this process on a biotechnological scale, namely the production of recombinant Leloir-glycosyltransferases and the availability of enzymes for the synthesis of nucleotide sugars (the glycosyltransferase donor substrates). The present review surveys some synthetic targets which have attracted the interest of glycobiologists as well as recombinant expression systems which give Leloir-glycosyltransferase activities in the mU and U range. The main part summarizes publications concerned with the complex pathways of primary and secondary nucleotide sugars and the availability and use of these enzymes for synthesis applications. In this context, a survey of our work will demonstrate how enzymes from different sources and pathways can be combined for the synthesis of nucleotide deoxysugars and oligosaccharides.

A highly practical synthesis of the sialyl Lewis X pentasaccharide and an investigation of binding to E-, P-, and L-selectins

A practical synthesis of the sialyl Lewis X (sLex) pentasaccharide, NeuAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta OEt (1), as a potential blocker for E-selectin has been described. The glycosylation of a trisaccharide acceptor, Fuc alpha (1-3)GlcNAc beta (1-3)Gal beta OEt, with a disaccharide donor, NeuAc alpha (2-3)Gal beta SMe, did not yield the desired sLex pentasaccharide 1 at all. However, the glycosylation of a disaccharide acceptor, GlcNAc beta (1-3)Gal beta OEt, with a disaccharide donor, NeuAc alpha (2-3)Gal beta SMe, quantitatively yielded the tetrasaccharide NeuAc alpha (2-3)Gal beta (1-4)GlcNAc beta (1-3)Gal beta OEt. This tetrasaccharide is readily converted to the title compound in a high yield by fucosylation, followed by deprotection. The inhibitory activities of compound 1 toward the binding of the natural ligand (sLex) with the E-, P-, and L-selectins were stronger than those of the sLex tetrasaccharide.

Use of human-milk fucosyltransferase in the chemoenzymic synthesis of analogues of the sialyl Lewis(a) and sialyl Lewis(x) tetrasaccharides modified at the C-2 position of the reducing unit

Two series of trisaccharides, having the formulas alpha-Neu5Ac-(2-->3)-beta-D-Gal-(1-->4)-beta-D-GlcZ-OR and alpha-Neu5Ac-(2-->3)-beta-D-Gal-(1-->3)-beta-D-GlcZ-OR [R = (CH2)8CO2CH3] respectively, in which the 2-deoxy substituent Z is azido, amino, propionamido, or acetamido, were prepared by chemical synthesis. Both types of modified trisaccharides are acceptors for a fucosyltransferase preparation obtained from human milk. Preparative fucosylations using this enzyme provided analogues of the sialyl Lewis(x) and sialyl Lewis(a) tetrasaccharide structures, which have been proposed to be ligands for cell-adhesion molecules. These syntheses further demonstrate the utility of glycosyltransferases in the preparation of oligosaccharide analogues.

Efficient enzymatic synthesis of the sialyl-Lewisx tetrasaccharide. A ligand for selectin-type adhesion molecules

Sialyl-Lewisx (NeuAc alpha 2-->3Gal beta 1-->4[Fuc alpha 1-->3]GlcNAc] has been identified as a ligand for E-selectin, P-selectin and recently also for L-selectin. We have synthesized the sialyl-Lewisx tetrasaccharide by total enzymatic synthesis from N-acetyllactosamine using a placental alpha 2-->3-sialyltransferase specific for type-2 chain acceptors, followed by a cloned human alpha 1-->3-fucosyltransferase (FucTV, the 'plasma-type' enzyme). This procedure resulted in the tetrasaccharide in a 61% overall yield.

Enzyme-catalyzed oligosaccharide synthesis

Cell-surface carbohydrates and their conjugates are involved in many types of molecular recognition. This review describes recent developments in enzyme-catalyzed oligosaccharide synthesis, with particular focus on glycosyltransferase and glycosidase reactions. With the increasing availability of glycosyltransferases via recombinant DNA technology, glycosyltransferase-catalyzed glycosylation with in situ regeneration of sugar nucleotides appears to be the most effective method for large-scale stereocontrolled oligosaccharide synthesis.