Reaction: Addition of a second 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 second mannose is added to the N-glycan precursor via an alpha-1,3 linkage. The reaction is catalyzed by the mannosyltransferase ALG2. This is a bifunctional enzyme with both alpha 1,3- and alpha 1,6-mannosyltransferase activities. In humans, only the alpha 1,3 activity used in this reaction has been elucidated (Thiel et al. 2003). Defects in ALG2 are the cause of ALG2-CDG (CDG-1i; MIM:607906) (Thiel et al. 2003).
Reaction - small molecule participants:
(GlcNAc)2 (Man)2 (PP-Dol)1 [integral component of cytoplasmic side of endoplasmic reticulum membrane]
GDP [cytosol]
GDP-Man [cytosol]
MDCDD [integral component of cytoplasmic side of endoplasmic reticulum membrane]
Reactome.org reaction link: R-HSA-446208
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Reaction input - small molecules:
GDP-alpha-D-mannose(2-)
beta-D-mannosyldiacetylchitobiosyldiphosphodolichol
Reaction output - small molecules:
alpha-D-Man-(1->6)-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-D-GlcNAc(PP-Dol)
GDP(3-)
Reactome.org link: R-HSA-446208