2.4.1.261: dolichyl-P-Man:Man8GlcNAc2-PP-dolichol alpha-1,2-mannosyltransferase
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For detailed information about dolichyl-P-Man:Man8GlcNAc2-PP-dolichol alpha-1,2-mannosyltransferase, go to the full flat file.
Reaction
Synonyms
ALG9, ALG9 alpha1,2 mannosyltransferase, ALG9 mannosyltransferase, dolichylphosphomannose-dependent ALG9 mannosyltransferase, EBS3, EC 2.4.1.130
ECTree
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General Information
General Information on EC 2.4.1.261 - dolichyl-P-Man:Man8GlcNAc2-PP-dolichol alpha-1,2-mannosyltransferase
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malfunction
physiological function
inactivation of Alg9 results in impaired maturation and defective glycosylation of polycystin-1
an ALG9-defective (congenital disorders of glycosylation type IL) patient who is homozygous for the p.Y286C (c.860A>G) mutation. This patient presents with psychomotor retardation, axial hypotonia, epilepsy, failure to thrive, inverted nipples, hepatomegaly, and pericardial effusion. Due to the ALG9 deficiency, the cells of this patient accumulated the lipid-linked oligosaccharides Man6GlcNAc2-PP-dolichol and Man8GlcNAc2-PP-dolichol. Lipid-linked Man6GlcNAc2 and Man8GlcNAc2 are transferred onto proteins with the same efficiency. In addition, glycoproteins bearing these Man6GlcNAc2 and Man8GlcNAc2 structures efficiently enter in the glucosylation/deglucosylation cycle of the quality control system to assist in protein folding. In comparison with control cells, patients cells degrade misfolded glycoproteins at an increasing rate. The Man8GlcNAc2 isomer C on the patients glycoproteins is found to promote the degradation of misfolded glycoproteins
malfunction
congenital disorders of glycosylation, a deficiency of the ALG9 alpha1,2 mannosyltransferase enzyme, causes an accumulation of lipid-linked-GlcNAc2Man6 and -GlcNAc2Man8 structures, which is paralleled by the transfer of incomplete oligosaccharide precursors to protein. A homozygous point-mutation E523K is detected in the ALG9 gene. The ALG9 defect found in the patient with congenital disorders of glycosylation, who presents with developmental delay, hypotonia, seizures, and hepatomegaly, shows that efficient lipid-linked oligosaccharide synthesis is required for proper human development and physiology