Reaction: Addition of a third mannose to the N-glycan precursor by ALG2
- in pathway: Biosynthesis of the N-glycan precursor (dolichol lipid-linked oligosaccharide, LLO) and transfer to a nascent protein
A third mannose is added to the N-glycan precursor by ALG2 using its alpha1,6-mannosyltransferase activity. This has been demonstrated experimentally in yeast (O'Reilly MK et al, 2006; Kämpf M et al, 2009); the human reaction is inferred by homology. Defects in ALG2 are the cause for CDG1I (Thiel C et al, 2003).
Reaction - small molecule participants:
(GlcNAc)2 (Man)3 (PP-Dol)1 [integral component of cytoplasmic side of endoplasmic reticulum membrane]
GDP [cytosol]
(GlcNAc)2 (Man)2 (PP-Dol)1 [integral component of cytoplasmic side of endoplasmic reticulum membrane]
GDP-Man [cytosol]
Reactome.org reaction link: R-HSA-449718
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Reaction input - small molecules:
alpha-D-Man-(1->6)-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-D-GlcNAc(PP-Dol)
GDP-alpha-D-mannose(2-)
Reaction output - small molecules:
alpha-D-Man-(1->3)-[alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-2-alpha-D-GlcNAc(PP-Dol)
GDP(3-)
Reactome.org link: R-HSA-449718