Synthesis of Phenoxyundecyl Diphosphate Disaccharides for Studies of the Biosynthesis of O Antigenic Polysaccharides in Enteric Bacteria

The biosynthesis of O antigenic polysaccharides in enteric bacteria from nucleoside diphosphate sugars (donor substrates) is catalyzed by the corresponding glycosyltransferases and proceeds through the intermediate formation of undecaprenyl diphosphate sugars (acceptor substrates). To study this process, a chemical synthesis of the compounds having the natural structure or their modified analogs is necessary. The phosphoroimidazolidate method is a universal method for synthesis of lipid diphosphate disaccharides containing 2-acetamido-2-deoxyglycosyl residue at the reducing end of the disaccharide moiety and 11-phenoxyundecyl residue as lipid fragment of the molecule. We report here protocols to synthesize the disaccharides P¹-(11-phenoxyundecyl)-P²-(2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate [D-Rha(α1-3)-D-GlcNAcα-PP-PhU, Compound 1] and P¹-(11-phenoxyundecyl)-P²-(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl) diphosphate [D-Gal(β1-3)-D-GalNAcα-PP-PhU, Compound 6]. We describe the procedures for identification and structure estimation of compounds by TLC, NMR, and MS. We also include the biochemical testing of Compound 6 with α2,3-sialyltransferase WbwA from Escherichia coli O104.

Synthesis of P1-(11-phenoxyundecyl)-P2-(2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate and P1-(11-phenoxyundecyl)-P2-(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl) diphosphate for the investigation of biosynthesis of O-antigenic polysaccharides in Pseudomonas aeruginosa and Escherichia coli O104

Two new phenoxyundecyl diphosphate sugars were synthesized for the first time: P¹-(11-phenoxyundecyl)-P²- (2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate and P¹-(11-phenoxyundecyl)-P²-(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl) diphosphate to study the third step of biosynthesis of the repeating units of O-antigenic polysaccharides in Pseudomonas aeruginosa and E.coli O104 respectively.

Identification and biochemical characterization of a novel α-1,3-mannosyltransferase WfcD from Escherichia coli O141

Glycosyltransferases (GTs) catalyze the formation of regio- and stereospecific glycosidic linkages between specific sugar donors and recipients. In this study, the function of the wfcD gene from the Escherichia coli O141 O-antigen gene cluster encoding an α-1,3-mannosyltransferase that catalyzed the formation of the linkage Man(α1-3)-GlcNAc was biochemically characterized. WfcD was expressed in E. coli BL21 (DE3), and the enzymatic product was identified by liquid chromatography-mass spectrometry (LC-MS), collision-induced dissociation electrospray ionization ion trap multiple tandem MS (CID-ESI-IT-MSⁿ) and glycosidase digestion using the donor substrate GDP-Man and the synthetic acceptor substrate decyl diphosphate 2-acetamido-2-deoxy-α-D-glucopyranose (GlcNAc-PP-De). The kinetic and physiochemical properties and the substrate specificity of WfcD were investigated. WfcD is the first characterized bacterial mannosyltransferase that acts on the Man(α1-3)-GlcNAc linkage. This study enhances our knowledge of the diverse functions of GTs.

[The synthesis of P1-[11-(anthracen-9-ylmethoxy)undecyl]-P2(2-Acetamido-2-deoxy-α-D-glucopyranosyl) diphosphate and the study of its acceptor properties in the enzymic reaction catalyzed by D-rhamnosyltransferase from Pseudomonas aeruginosa]

P1-[11-(Anthracen-9-ylmethoxy)undecyl]-P2-(2-acetamido-2-deoxy-α-D-glucopyranosyl) diphosphate, a fluorescent derivative of undecyl diphosphate 2-acetamido-2-deoxyglucose, was chemically synthesized. The ability of the compound to serve as acceptor substrate of D-rhamnose residue in the enzymatic reaction catalyzed by D-rhamnosyltransferase from Pseudomonas aeruginosa PAO1 was demonstrated.

[Synthesis of 11-[(2-pyridyl)amino]- and 11-[(9-anthracenylcarbonyl)amino]undecyl phosphate and investigation of their acceptor properties in the enzymic reaction catalyzed by galactosylphosphotransferases from Salmonella]

11-[(2-Pyridyl)amino]undecyl phosphate and 11-[(9-anthracenylcarbonyl)amino]undecyl phosphate were chemically synthesized. The abiliy of these new fluorescent derivatives of undecyl phosphate to serve as acceptor substrate of galactosyl phosphate residue in the enzymic reaction catalyzed by galactosylphosphotransferase from Salmonella anatum or Salmonella newport membrane preparation was demonstrated.

[Synthesis and acceptor properties of 11-[(9'-anthracenyl)methoxy]undecyl phosphate and P1-{11-[(9'-anthracenyl)methoxy]undecyl}-P2-(alpha-D-galactopyranosyl) diphosphate in the enzymic reactions catalyzed by galactosylphosphotransferase and mannosyltransferase from Salmonella newport]

Fluorescent 11-[(9'-anthracenyl)methoxy]undecyl phosphate and P1-{11-[(9'-anthracenyl)methoxy]undecyl}-P2-(alpha-D-galactopyranosyl) diphosphate were chemically synthesized for the first time. The ability of the first compound to serve as substrate-acceptor ofgalactosyl phosphate residue and the second compound of mannosyl residue in enzymic reactions catalyzed by galactosylphosphotransferase and mannosyltransferase from Salmonella newport membrane preparation was demonstrated.

Functional identification of bacterial glucosyltransferase WbdN

The outer membrane of gram-negative bacteria is stabilized by lipopolysaccharides (LPS). The O-antigenic polysaccharides of LPS are composed of repeating units that are exposed to and can interact with the environment. The glycosyltransferases that assemble these repeating units are encoded by the O-antigen gene cluster and utilize undecaprenol-phosphate-linked intermediates as natural acceptor substrates, and nucleotide sugars as donor substrates on the cytoplasmic face of the inner membrane. Many of the glycosyltransferase genes are known but the enzymatic functions of most of them remain to be identified. We describe here how the function of a recombinant glucosyltransferase WbdN from Escherichia coli O157 can be determined by NMR analysis of the enzyme product, using a synthetic acceptor substrate analog. A fluorescent acceptor substrate analog can be used in highly sensitive enzyme assays that allow the characterization of enzyme activity without the use of radioactive nucleotide sugar donor substrates.

[Synthesis of p(1)-(11-phenoxyundecyl)-P(2)-(alpha-D-galactopyranosyl) diphosphate and p(1)-(11-phenoxyundecyl)-P(2)-(alpha-D-glucopyranosyl) diphosphate; assay of their acceptor properties for mannosyl residue in the enzmic reaction catalyzed by mannosyltransferase from Salmonella newport]

P(1)-(Phenoxyundecyl)-P(2)-(alpha-D-galactopyranosyl) diphosphate as well as P(1)-(11-phenoxyundecyl)-P(2)-(alpha-D-glucopyranosyl) diphosphate are newly synthesized and their ability to serve as substrate-acceptor of mannosyl residue in enzymic reaction catalyzed by mannosyltransferase from Salmonella newport membrane preparation is investigated. The possibility ofgalactosyl-containing derivative to serve as mannosyl acceptor from GDP-Man is established whereas glucosyl-containing compound is inactive in this process.

Biochemical characterization of WbdN, a β1,3-glucosyltransferase involved in O-antigen synthesis in enterohemorrhagic Escherichia coli O157

The enterohemorrhagic O157 strain of Escherichia coli, which is one of the most well-known bacterial pathogens, has an O-antigen repeating unit structure with the sequence [-2-d-Rha4NAcα1-3-l-Fucα1-4-d-Glcβ1-3-d-GalNAcα1-]. The O-antigen gene cluster of E. coli O157 contains the genes responsible for the assembly of this repeating unit and includes wbdN. In spite of cloning many O-antigen genes, biochemical characterization has been done on very few enzymes involved in O-antigen synthesis. In this work, we expressed the wbdN gene in E. coli BL21, and the His-tagged protein was purified. WbdN activity was characterized using the donor substrate UDP-[(14)C]Glc and the synthetic acceptor substrate GalNAcα-O-PO(3)-PO(3)-(CH(2))(11)-O-Ph. The enzyme product was isolated by high pressure liquid chromatography, and mass spectrometry showed that one Glc residue was transferred to the acceptor by WbdN. Nuclear magnetic resonance analysis of the product structure indicated that Glc was β1-3 linked to GalNAc. WbdN contains a conserved DxD motif and requires divalent metal ions for full activity. WbdN activity has an optimal pH between 7 and 8 and is highly specific for UDP-Glc as the donor substrate. GalNAcα derivatives lacking the diphosphate group were inactive as substrates, and the enzyme did not transfer Glc to GlcNAcα-O-PO(3)-PO(3)-(CH(2))(11)-O-Ph. Our results illustrate that WbdN is a specific UDP-Glc:GalNAcα-diphosphate-lipid β1,3-Glc-transferase. The enzyme is a target for the development of inhibitors to block O157-antigen synthesis.