Glycosyltransferases for biosynthesis of oligosaccharides, and genes encoding them

Abstract

The present invention is directed to nucleic acids encoding glycosyltransferases, the proteins encoded thereby, and to methods for synthesizing oligosaccharides using the glycosyltransfereses of the invention. In particular, the present application is directed to identification a glycosyltransferase locus of Neisseria gonorrhoeae containing five open reading frames for five different glycosyltransferases. The functionally active glycosyltransferases of the invention are characterized by catalyzing reactions such as adding Gal β1→4 to GlcNAc or Glc; adding GalNAc or GlcNAc β1→3 to Gal; and adding Gal α1→4 to Gal. The glycosyltransferases of the invention are particularly suited to the synthesis of the oligosaccharides Galβ1→4GlcNAcβ1→3Galβ1→4Glc (a mimic of lacto-N-neotetraose), GalNAcβ1→3Galβ1→4GlcNAcβ1→3Galβ1→4Glcβ1→4 (a mimic a ganglioside), and Galα1→4Galβ1→4Glcβ1→4Hep→R (a mimic of the saccharide portion of globo-glycolipids).

Description

[0001] The research leading to the present invention was supported in part with funds from grant number AI-10615 from the Public Health Service. Accordingly, the Government may have certain rights in the invention.FIELD OF THE INVENTION [0002] The present invention relates to glycosyltransferases useful for biosynthesis of oligosaccharides, genes encoding such glycosyltransferases and recombinant methods of producing the enzymes, and the oligosaccharides produced thereby. BACKGROUND OF THE INVENTION Neisseria and Lipo-oligosaccharide (LOS) [0003] While Neisseria species commonly colonize many mammalian hosts, human beings are the only species subject to invasive disease by members of this species. Neisseria meningitidis is the etiologic agent for septicemia and meningitis that may occur in epidemic form. Neisseria gonorrhoeae is the causative agent of gonorrhea and its manifold complications. These organisms, particularly the gonococcus, have proved remarkably adept at varying the a...

AI Technical Summary

Benefits of technology

[0027] An important advantage of the present invention is that it provides for the synthesis of oligosaccharide antigens of Neisseria independently of lipid A, which is highly toxic. Use of the natural LOS from Neisseria, while theoretically desirable for vaccine preparation, fails. The lipid A portion of LOS is a potent endotoxin, and highly toxic. Chemical treatment of the LOS, e.g., by hydrolysis. destroys the antigenicity of the oligosaccharide, leaving a useless product. Thus, it is highly desirable to have a source of Neisseria oligosaccharides attached to non-toxic lipids for vaccine preparation.

[0028] Thus, the invention provides glycosyltransferases and strategies for preparing a number of oligosaccharides, such as but not limited to, Galα1→4Galβ1→4Glc, Galβ1→4GlcNAcβ1→3Galβ1→4Glc, and GalNAcβ1→3Galβ1→4GlcNAcβ1→3Galβ1→4Glc.

[0029] Accordingly, it is a primary object of the invention to provide glycosyltransferases useful for the synthesis of oligosaccharides.

[0030] It is a further object of the invention to provide for the synthesis of oligosaccharides characteristic of Neisseria meningitidis and N. gonorrhoeae.

[0031] It is a further object of the invention to provide for the synthesis of oligosaccharides characteristic of mammalian oligosaccharides, including blood group core oligosaccharides.

[0032] It is still a further object of the invention to provide for vaccines having the oligosaccharide unit of LOS, but lacking lipid. A.

Problems solved by technology

In the case of Neisseria gonorrhoeae, antigenic variability is so pronounced that a serological classification scheme has proved elusive.

Because of the molecular heterogeneity and antigenic variation of the LOS produced by gonococci the determination of the structural chemistry of this antigen has proved to be a difficult problem, and definitive information based on very sophisticated analyses has only recently become available (Yamasaki et al, 1991, Biochemistry 30:10566; Kerwood et al., 1992, Biochemistry 31:12760; John et al., 1991, J. Biol. Chem. 266:19303; Gibson et al., 1993, J. Bacteriol. 175:2702).

Numerous classical techniques for the synthesis of carbohydrates have been developed, but these techniques suffer the difficulty of requiring selective protection and deprotection.

Organic synthesis of oligosaccharides is further hampered by the lability of may glycosidic bonds, difficulties in achieving regio-selective sugar coupling, and generally low synthetic yields.

In short, unlike the experience with peptide synthesis, traditional synthetic organic chemistry cannot provide for quantitative, reliable synthesis of even fairly simple oligosaccharides.

Thus, synthesis of a desired oligosaccharide may be limited by the availability of glycosyltransferases (see, Roth, International Patent Publication No.

Another drawback of biosynthesis is that the glycosyltransferases themselves are usually present in fairly low quantities in cells.

It is difficult to obtain enough of the enzyme to be commercially practicable.

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