| Entry |
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| Name |
N-Glycan biosynthesis
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| Description |
N-glycans or asparagine-linked glycans are major constituents of glycoproteins in eukaryotes. N-glycans are covalently attached to asparagine with the consensus sequence of Asn-X-Ser/Thr by an N-glycosidic bond, GlcNAc b1- Asn. Biosynthesis of N-glycans begins on the cytoplasmic face of the ER membrane with the transferase reaction of UDP-GlcNAc and the lipid-like precursor P-Dol (dolichol phosphate) to generate GlcNAc a1- PP-Dol. After sequential addition of monosaccharides by ALG glycosyltransferases [MD: M00055], the N-glycan precursor is attached by the OST (oligosaccharyltransferase) complex to the polypeptide chain that is being synthesized and translocated through the ER membrane. The protein-bound N-glycan precursor is subsequently trimmed, extended, and modified in the ER and Golgi by a complex series of reactions catalyzed by membrane-bound glycosidases and glycosyltransferases. N-glycans thus synthesized are classified into three types: high-mannose type, complex type, and hybrid type. Defects in N-glycan biosynthesis lead to a variety of human diseases known as congenital disorders of glycosylation [DS: H00118 H00119].
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| Class |
Metabolism; Glycan biosynthesis and metabolism
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| Pathway map |
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| Module |
| N-glycan precursor biosynthesis [PATH: map00510] | | Oligosaccharyltransferase [PATH: map00510] | | N-glycan precursor trimming [PATH: map00510] | | N-glycan biosynthesis, high-mannose type [PATH: map00510] | | N-glycan biosynthesis, complex type [PATH: map00510] |
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| Disease |
| Congenital disorders of glycosylation (CDG) type I | | Congenital disorders of glycosylation (CDG) type II | | Nonsyndromic autosomal recessive mental retardation (NS-ARMR) |
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| Other DBs |
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| Reference |
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| Authors |
Schutzbach JS. |
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| Title |
The role of the lipid matrix in the biosynthesis of dolichyl-linked oligosaccharides. |
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| Journal |
Glycoconj J 14:175-82 (1997) |
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| Reference |
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| Authors |
Oriol R, Martinez-Duncker I, Chantret I, Mollicone R, Codogno P. |
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| Title |
Common origin and evolution of glycosyltransferases using Dol-P-monosaccharides as donor substrate. |
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| Journal |
Mol Biol Evol 19:1451-63 (2002) |
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| Reference |
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| Authors |
Thiel C, Schwarz M, Peng J, Grzmil M, Hasilik M, Braulke T, Kohlschutter A, von Figura K, Lehle L, Korner C. |
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| Title |
A new type of congenital disorders of glycosylation (CDG-Ii) provides new insights into the early steps of dolichol-linked oligosaccharide biosynthesis. |
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| Journal |
J Biol Chem 278:22498-505 (2003) |
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| Reference |
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| Authors |
Cipollo JF, Trimble RB, Chi JH, Yan Q, Dean N. |
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| Title |
The yeast ALG11 gene specifies addition of the terminal alpha 1,2-Man to the Man5GlcNAc2-PP-dolichol N-glycosylation intermediate formed on the cytosolic side of the endoplasmic reticulum. |
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| Journal |
J Biol Chem 276:21828-40 (2001) |
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| Reference |
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| Authors |
Frank CG, Aebi M. |
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| Title |
ALG9 mannosyltransferase is involved in two different steps of lipid-linked oligosaccharide biosynthesis. |
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| Journal |
Glycobiology 15:1156-63 (2005) |
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| Reference |
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| Authors |
O'Reilly MK, Zhang G, Imperiali B. |
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| Title |
In vitro evidence for the dual function of Alg2 and Alg11: essential mannosyltransferases in N-linked glycoprotein biosynthesis. |
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| Journal |
Biochemistry 45:9593-603 (2006) |
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| KO pathway |
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