Wataru Sumiyoshi

Structural analysis of N-glycans of the planarian Dugesia japonica

To investigate the relationship between phylogeny and glycan structures, we analyzed the structure of planarian N‐glycans. The planarian Dugesia japonica, a member of the flatworm family, is a lower metazoan. N‐glycans were prepared from whole worms by hydrazinolysis, followed by tagging with the fluorophore 2‐aminopyridine at their reducing end. The labeled N‐glycans were purified, and separated by three HPLC steps. By comparison with standard pyridylaminated N‐glycans, it was shown that the N‐glycans of planarian include high mannose‐type and pauci‐mannose‐type glycans. However, many of the major N‐glycans from planarians have novel structures, as their elution positions did not match those of the standard glycans. The results of mass spectrometry and sugar component analyses indicated that these glycans include methyl mannoses, and that the most probable linkage was 3‐O‐methylation. Furthermore, the methyl residues on the most abundant glycan may be attached to the non‐reducing‐end mannose, as the glycans were resistant to α‐mannosidase digestion. These results indicate that methylated high‐mannose‐type glycans are the most abundant structure in planarians.

Production of heterologous glycoproteins by a glycosylation-defective alg3och1 mutant of Schizosaccharomyces pombe.

The early stages of N-linked glycosylation are highly conserved between fungal and mammalian cells. Such N-linked oligosaccharides are synthesized through the ordered assembly of a dolichyl pyrophosphate (Dol-PP)-linked Glc(3)Man(9)GlcNAc(2) structure by the sequential actions of several glycosyltransferases located in the endoplasmic reticulum (ER). Of the glycosyltransferase genes, Saccharomyces cerevisiae ALG3 has been identified to encode the Dol-P-Man:Man(5)GlcNAc(2)-PP-Dol α1,3-mannosyltransferase, and an alg3 mutant has been shown to accumulate an Endo H-resistant M5B (Manα1,2-Manα1,2-Manα1,3(Manα1,6-)-Manβ1,4-GlcNAcβ1,4-GlcNAc) structure. Although Schizosaccharomyces pombe contains a homolog of the ALG3 gene (SPAC7D4.06c), the role of this gene in oligosaccharide biosynthesis is not at all clear. In this study, we deleted the alg3(+) gene in the och1Δ mutant and analyzed the detailed oligosaccharide structures in alg3Δoch1Δ double mutant. The oligosaccharides were prepared from cell-surface glycoproteins by hydrazinolysis and fluorescent labeling with 2-aminopyridine. The labeled oligosaccharides were analyzed by high performance liquid chromatography, in combination with sequential glycosidase digestion and methylation analysis. These analyses revealed that the N-linked oligosaccharides of S. pombe alg3Δoch1Δ cells mainly consisted of two or three α-galactose-capped M5B structures. Finally, western blot analysis of recombinant human transferrin suggested that heterologously expressed glycoproteins in alg3Δoch1Δ cells have Endo H-resistant N-linked oligosaccharide structures similar to those of alg3Δoch1Δ cell-surface glycoproteins.

Development of an amperometric flow analysis sensor for specific detection of D-psicose

The aim of this study was to develop a simple, rapid and highly sensitive sensor for measuring the rare sugar d-psicose. The proposed system adopts amperometric flow analysis and two consecutive enzyme reactions consisting of a reactor packed with d-tagatose 3-epimerase (DTE)-immobilized beads, which converts d-psicose to d-fructose, and a carbon-paste electrode containing d-fructose dehydrogenase (DFDH). In order to fabricate a robust sensor system, various experimental parameters were optimized including the buffer composition, flow rate for the two enzyme reactions and the size of micro-flow cell. The developed sensor responded linearly to d-psicose concentration in the range from 0.08 to 50mM (R(2)=0.988). The signal/noise ratio was 3.0 for the 0.08 mM d-psicose solution, and the relative standard deviations were 1.7 (n=20) and 2.6% (n=20) for the 10 and 20mM d-psicose solutions, respectively. One round of assay was completed within 8 min. Our results suggest that the sensor can be used not only for the detection of d-psicose in food samples but also for monitoring d-psicose within the environment. Moreover, the sensor system can be applied to the detection of many other rare sugars by using the same measurement principle.

Strategic Glycan Elution Map for the Production of Human-Type N-Linked Oligosaccharides: The Case of Hen Egg Yolk and White

Glycans play important roles in various biological phenomena, but the lack of a systematic procedure for producing complex structures of glycans severely restricts their application in the medical and industrial fields. In this paper, we propose a basic strategy for the preparation of substantial amounts (>100 mg) of N-linked oligosaccharides, where the structure of each glycan is mapped with its elution position in liquid chromatography as well as the empirical yield. In model experiments using hen egg white and yolk as starting materials, the former provided a series of agalactosylated complex-type and hybrid-type N-linked oligosaccharides containing bisecting N-acetylglucosamine (GlcNAc) in addition to two high-mannose type glycans. In contrast, egg yolk gave predominantly α2-6sialylated biantennary glycans together with a high-mannose type one, reflecting the difference in the origins of the tissues. Due to the total identity of the glycans obtained to human ones, the present strategy should provide a practical scheme for the production of human-type N-linked oligosaccharides.

Improved Method for Drawing of a Glycan Map, and the First Page of Glycan Atlas, Which Is a Compilation of Glycan Maps for a Whole Organism

Glycan Atlas is a set of glycan maps over the whole body of an organism. The glycan map that includes data of glycan structure and quantity displays micro-heterogeneity of the glycans in a tissue, an organ, or cells. The two-dimensional glycan mapping is widely used for structure analysis of N-linked oligosaccharides on glycoproteins. In this study we developed a comprehensive method for the mapping of both N- and O-glycans with and without sialic acid. The mapping data of 150 standard pyridylaminated glycans were collected. The empirical additivity rule which was proposed in former reports was able to adapt for this extended glycan map. The adapted rule is that the elution time of pyridylamino glycans on high performance liquid chromatography (HPLC) is expected to be the simple sum of the partial elution times assigned to each monosaccharide residue. The comprehensive mapping method developed in this study is a powerful tool for describing the micro-heterogeneity of the glycans. Furthermore, we prepared 42 pyridylamino (PA-) glycans from human serum and were able to draw the map of human serum N- and O-glycans as an initial step of Glycan Atlas editing.

Structural analysis of α1,3-linked galactose-containing oligosaccharides in Schizosaccharomyces pombe mutants harboring single and multiple α-galactosyltransferase genes disruptions

In the fission yeast Schizosaccharomyces pombe, galactose (Gal) residues are transferred to N- and O-linked oligosaccharides of glycoproteins by galactosyltransferases in the lumen of the Golgi apparatus. In S. pombe, the major in vitro α1,2-galactosyltransferase activity has been purified, the gma12(+) gene has been cloned, and three α-galactosyltransferase genes (gmh1(+)-gmh3(+)) have also been partially characterized. In this study, we found three additional uncharacterized genes with homology to gmh1(+) (gmh4(+)-gmh6(+)) in the fission yeast genome sequence. All possible single disruption mutants and the septuple disruption strain were constructed and characterized. The electrophoretic mobility of acid phosphatase prepared from gma12Δ, gmh2Δ, gmh3Δ and gmh6Δ mutants was higher than that from wild type, indicating that Gma12p, Gmh2p, Gmh3p and Gmh6p are required for the galactosylation of N-linked oligosaccharides. High-performance liquid chromatography (HPLC) analysis of pyridylaminated O-linked oligosaccharides from each single mutant showed that Gma12p, Gmh2p and Gmh6p are involved in galactosylation of O-linked oligosaccharides. The septuple mutant exhibited similar drug and temperature sensitivity as a gms1Δ mutant that is incapable of galactosylation. Oligosaccharide structural analysis based on HPLC and methylation analysis revealed that the septuple mutant still contained oligosaccharides consisting of α1,3-linked Gal residues, indicating that an unknown α1,3-galactosyltransferase activity was still present in the septuple mutant.

Development of a chemical strategy to produce rare aldohexoses from ketohexoses using 2-aminopyridine

Rare sugars are monosaccharides that are found in relatively low abundance in nature. Herein, we describe a strategy for producing rare aldohexoses from ketohexoses using the classical Lobry de Bruyn-Alberda van Ekenstein transformation. Upon Schiff-base formation of keto sugars, a fluorescence-labeling reagent, 2-aminopyridine (2-AP), was used. While acting as a base catalyst, 2-AP efficiently promoted the ketose-to-aldose transformation, and acting as a Schiff-base reagent, it effectively froze the ketose-aldose equilibrium. We could also separate a mixture of Sor, Gul, and Ido in their Schiff-base forms using a normal-phase HPLC separation system. Although Gul and Ido represent the most unstable aldohexoses, our method provides a practical way to rapidly obtain these rare aldohexoses as needed.

A comprehensive HPLC analytical system for the identification and quantification of hexoses that employs 2-aminobenzamide coupling

Rare sugars are defined as monosaccharides with extremely low natural abundances. Their natural distributions and biological functions remain to be clarified. To establish a robust analytical system that can separate, identify and quantify rare sugars, 12 d-hexoses-including five rare aldohexoses and three rare ketohexoses-were labelled with 2-aminobenzamide (2-AB), and the fluorescently tagged monosaccharides were separated by high-performance liquid chromatography (HPLC). Because the ketohexoses were much less reactive than were the aldohexoses, the reaction conditions were optimized to achieve the maximum yields (>75%) for both aldohexoses and ketohexoses. The calibration curve determined for the rare ketohexose, d-psicose (Psi), was linear between 1 pmol and 1 micromol and had a correlation coefficient of 0.9999. Using the developed method, the psicose content in a leaf of Itea virginica, in which the presence of psicose has previously been reported, was found to be 2.7 mg psicose/g leaf. The result proved feasibility of the method even for natural products. Because the system is a comprehensive tool, it should help answer questions concerning the biosyntheses and functions of rare hexose sugars.

Comprehensive analysis of N-linked oligosaccharides from eggs of the family Phasianidae.

We have reported a strategic procedure for the preparation of human-type N-linked oligosaccharides targeting hen egg white and yolk. To determine whether the technique is applicable to other avian species, we performed comparative analysis of N-linked oligosaccharides derived from eggs of other pheasant species. Our investigation of the principal oligosaccharides resulted in several major findings: (i) Glycan profiles as well as total yields were different between species and tissues (egg white and yolk). (ii) A common feature of egg white glycans is agalactosylated, hybrid-type, and complex-type oligosaccharides containing bisecting GlcNAc as major components. (iii) Egg yolk of pheasant species contained α2-6sialylated, biantennary complex-type oligosaccharides as major components. (iv) Egg yolk of Japanese pheasant and golden pheasant contained unusual persialylated oligosaccharides. Our results suggest that pheasant egg glycomes are significantly different from other avian species, although some common features are present.

Hypersialylated type-I lactosamine-containing N-glycans found in Artiodactyla sera are potential xenoantigens

There is increasing interest in biologics, i.e. human-originated biological pharmaceutics. Most of the protein drugs developed so far, such as immunoglobulins and erythropoietin, are secreted glycoproteins; as a result, any non-human-type glycans, such as αGal and NeuGc, derived from animal cells and sera must be removed to circumvent undesirable immunogenic reactions. In this study, we made an extensive search for potential xenoantigenic glycans among a panel of mammalian sera. As a result, sera belonging to the order Artiodactyla, i.e. bovine, lamb and goat sera, were found to contain substantial amounts of hypersialylated biantennary glycans closely associated with a type-I lactosamine structure containing a unique tetrasaccharide, Siaα2-3Galβ1-3(Siaα2-6)GlcNAc. In all three Artiodactyla sera, the most abundant structure was Siaα2-3Galβ1-3(Siaα2-6)GlcNAcβ1-2Manα1-3[Siaα2-6Galβ1-4GlcNAcβ1-2Manα1-6]Manβ1-4GlcNAcβ1-4GlcNAc. A dually hypersialylated biantennary structure, Siaα2-3Galβ1-3(Siaα2-6)GlcNAcβ1-2Manα1-3[Siaα2-3Galβ1-3(Siaα2-6)GlcNAcβ1-2Manα1-6]Manβ1-4GlcNAcβ1-4GlcNAc, was also abundant (10%) in bovine serum. The amount of hypersialylated glycans among total sialylated glycans was 46, 26 and 23% in bovine, lamb and goat sera, respectively. On the other hand, such structures could not be detected in the sera of other animals including human. The biological functions and the immunogenicity of the hypersialylated glycans in these animals remain to be elucidated; however, it is worth noting that glycoproteins biosynthesized from Artiodactyla cells and those contaminated with bovine serum might enhance undesirable antigenicity in human patients.