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]

external resources
NCBI:82975
KEGG:hsa00510
PUBMED:12684507
PUBMED:16878994
PUBMED:11278778
PUBMED:9111134
PUBMED:12200473
PUBMED:15987956

genes
DAD1 , DDOST , DPAGT1 , FUT8 , B4GALT1 , STT3A , MAN1A1 , MAN2A2 , MAN2A1 , MGAT1 , MGAT2 , MGAT3 , MGAT5 , RPN1 , RPN2 , ST6GAL1 , MOGS , TUSC3 , B4GALT3 , B4GALT2 , DPM1 , DPM2 , ALG3 , MAN1A2 , MAN1B1 , MGAT4B , MGAT4A , DOLK , GANAB , MGAT4C , ALG5 , ALG6 , DPM3 , ALG1 , MAN1C1 , DOLPP1 , ALG8 , ALG12 , ALG9 , ALG13 , ST6GAL2 , ALG10 , ALG2 , ALG10B , MGAT5B , MGAT4D , ALG14 , STT3B , ALG11 ,