N-Glycan biosynthesis - Homo sapiens (human)

Curator(s): Joe Strothman

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, 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.    
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N-Glycan biosynthesis - Homo sapiens (human) cluster_node17 ER-GOLGI Dol node1 Dol->node1 node2 P-Dol node1->node2 node3 node2->node3 asparagine-linked glycosylation 5,dolichyl-phosphate beta-glucosyltransferase homolog (S. cerevisiae) ALG5 node2->ALG5 ALG7 node2->ALG7 node10 DPM1 DPM2 DPM3 node2->node10 node3->Dol node4 node4->node2 node6 PP-Dol node7 node6->node7 node7->node2 Terpinoid backbone biosynthesis Terpinoid backbone biosynthesis->node6 asparagine-linked glycosylation 11,alpha-1,2-mannosyltransferase homolog (yeast) ALG11 G10526 ALG11->G10526 G00006 ALG11->G00006 Fructose and mannose metabolism node9 Man-GDP Fructose and mannose metabolism->node9 node13 Various types of N-glycan biosynthesis G00001 node8 ALG13 ALG14 G00001->node8 G00003 asparagine-linked glycosylation 2,alpha-1,3-mannosyltransferase homolog (S. cerevisiae) ALG2 G00003->ALG2 G00004 G00004->ALG2 G00005 G00005->ALG11 G10526->ALG11 Protein asparagine STT OST Protein asparagine->STT node14 1 Keratan sulfate biosynthesis node15 G00017 node15->G00017 node16 G00017->node16 DS 3 node16->DS 3 asparagine-linked glycosylation 1,beta-1,4-mannosyltransferase homolog (S. cerevisiae) ALG1 ALG1->G00003 asparagine-linked glycosylation 10,alpha-1,2-glucosyltransferase homolog (S. pombe) ALG10 G00008 ALG10->G00008 G00008->STT asparagine-linked glycosylation 3,alpha-1,3- mannosyltransferase homolog (S. cerevisiae) ALG3 G00006->ALG3 asparagine-linked glycosylation 12,alpha-1,6-mannosyltransferase homolog (S. cerevisiae) ALG12 G10597 ALG12->G10597 asparagine-linked glycosylation 9,alpha-1,2-mannosyltransferase homolog (S. cerevisiae) ALG9 G10597->ALG9 G00002 node8->G00002 G00002->ALG1 ALG2->G00004 ALG2->G00005 G10595 ALG3->G10595 G10595->ALG9 node5 GlcBeta -P -Dol ALG5->node5 node5->node4 asparagine-linked glycosylation 6,alpha-1,3-glucosyltransferase homolog (S. cerevisiae) ALG6 node5->ALG6 G10598 ALG6->G10598 asparagine-linked glycosylation 8,alpha-1,3-glucosyltransferase homolog (S. cerevisiae) ALG8 G10598->ALG8 ALG7->G00001 G10599 ALG8->G10599 G10599->ALG10 G00007 ALG9->G00007 G10596 ALG9->G10596 G00007->ALG6 G10596->ALG12 node11 ManBeta -P -Dol node10->node11 node11->ALG3 node12 Glycosylphosphatidylinositol(GPI)-anchor biosynthesis node11->node12 fucosyltransferase 8 (alpha (1,6) fucosyltransferase) FUT8 G00016 FUT8->G00016 G00016->node15 node9->ALG1 node9->node10 STT->node6 G00009 STT->G00009 GCS1 G00009->GCS1 G00171 GCS1->G00171 G00011 G00011->node13 MAN1 G00011->MAN1 G00012 MAN1->G00012 mannosyl (alpha-1,3-)-glycoprotein beta-1,2-N-acetylglucosaminyltransferase MGAT1 G00012->MGAT1 G00013 MGAT1->G00013 MAN2 G00013->MAN2 MAN2->node14 MAN2 G00014 MAN2->G00014 mannosyl (alpha-1,6-)-glycoprotein beta-1,2-N-acetylglucosaminyltransferase MGAT2 G00014->MGAT2 G00015 MGAT2->G00015 G00015->Keratan sulfate biosynthesis G00015->FUT8 mannosyl (beta-1,4-)-glycoprotein beta-1,4-N-acetylglucosaminyltransferase MGAT3 G00015->MGAT3 MGAT4 G00015->MGAT4 G00019 MGAT3->G00019 G00020 MGAT4->G00020 mannosyl (alpha-1,6-)-glycoprotein beta-1,6-N-acetyl-glucosaminyltransferase MGAT5 G00020->MGAT5 G00021 MGAT5->G00021 mannosyl (alpha-1,3-)-glycoprotein beta-1,4-N-acetylglucosaminyltransferase,isozyme C (putative) MGAT4C G00021->MGAT4C G00022 MGAT4C->G00022 glucosidase,alpha; neutral AB GANAB G00171->GANAB GANAB->G00011 G00010 GANAB->G00010 print "