Chitobiosyldiphosphodolichol beta-mannosyltransferase (ALG1)

Chitobiosyldiphosphodolichol beta-mannosyltransferase (ALG1) is a key **glycosyltransferase enzyme** localized to the endoplasmic reticulum membrane, responsible for catalyzing the first mannosylation step in the synthesis of lipid-linked oligosaccharides (LLOs)—precursors for **N-glycosylation** of proteins. The ALG1 enzyme specifically transfers the first mannose residue onto the growing oligosaccharide chain attached to dolichol pyrophosphate, a necessary requirement for assembling the mature 14-sugar glycan that is transferred to asparagine residues of target proteins. Mutations in ALG1 result in **ALG1-CDG (congenital disorder of glycosylation type Ik)**, a rare autosomal recessive disorder characterized by defective glycoprotein biosynthesis, with clinical manifestations that often include severe developmental and neurological impairment. ALG1 deficiency leads to accumulation of incomplete glycan intermediates, broad hypoglycosylation of glycoproteins, and downstream effects on protein stability and cellular function. Glycoproteomic signatures, such as increased short oligosaccharide-bearing peptides, serve as emerging **biomarkers** for the diagnosis of ALG1-related disorders. No direct drug modulators or therapies currently exist targeting ALG1; treatment is predominantly supportive.

Other names

ALG1CDG1KHMAT1HMT-1HMT1MT-1Mat-1hMat-1chitobiosyldiphosphodolichol beta-mannosyltransferaseasparagine-linked glycosylation protein 1 homologbeta-1,4-mannosyltransferaseGDP-Man:GlcNAc2-PP-dolichol mannosyltransferaseGDP-mannose-dolichol diphosphochitobiose mannosyltransferasemannosyltransferase-1