ALG2
Function
Mannosyltransferase that operates in the biosynthetic pathway of dolichol-linked oligosaccharides, the glycan precursors employed in protein asparagine (N)-glycosylation. The assembly of dolichol-linked oligosaccharides begins on the cytosolic side of the endoplasmic reticulum membrane and finishes in its lumen. The sequential addition of sugars to dolichol pyrophosphate produces dolichol-linked oligosaccharides containing fourteen sugars, including two GlcNAcs, nine mannoses and three glucoses. Once assembled, the oligosaccharide is transferred from the lipid to nascent proteins by oligosaccharyltransferases. Catalyzes, on the cytoplasmic face of the endoplasmic reticulum, the addition of the second and third mannose residues to the dolichol-linked oligosaccharide chain, to produce Man3GlcNAc(2)-PP-dolichol core oligosaccharide. Man3GlcNAc(2)-PP-dolichol is a substrate for ALG11, the following enzyme in the biosynthetic pathway (PubMed:12684507, PubMed:35136180). While both alpha 1,3 and alpha 1,6 linkages are possible, the sequential addition of alpha 1,3 followed by alpha 1,6 is probably the preferred route (PubMed:35136180).
Involvement in disease
Congenital disorder of glycosylation 1I
CDG1I
A form of congenital disorder of glycosylation, a multisystem disorder caused by a defect in glycoprotein biosynthesis and characterized by under-glycosylated serum glycoproteins. Congenital disorders of glycosylation result in a wide variety of clinical features, such as defects in the nervous system development, psychomotor retardation, dysmorphic features, hypotonia, coagulation disorders, and immunodeficiency. The broad spectrum of features reflects the critical role of N-glycoproteins during embryonic development, differentiation, and maintenance of cell functions.
None
The disease is caused by variants affecting the gene represented in this entry.
Myasthenic syndrome, congenital, 14
CMS14
A form of congenital myasthenic syndrome, a group of disorders characterized by failure of neuromuscular transmission, including pre-synaptic, synaptic, and post-synaptic disorders that are not of autoimmune origin. Clinical features are easy fatigability and muscle weakness. CMS14 is an autosomal recessive form characterized by onset of limb-girdle muscle weakness in early childhood. The disorder is slowly progressive, and some patients may become wheelchair-bound.
None
The disease is caused by variants affecting the gene represented in this entry.
Pathway
Protein modification; protein glycosylation.
Sequence Similarities
Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 4 subfamily.
Cellular localization
- Endoplasmic reticulum membrane
- Single-pass membrane protein
- Active on cytoplasmic side of endoplasmic reticulum membrane.
Alternative names
UNQ666/PRO1298, ALG2, Asparagine-linked glycosylation protein 2 homolog, GDP-Man:Man(1)GlcNAc(2)-PP-dolichol mannosyltransferase