The ALG6 gene provides instructions for making an enzyme that is involved in a process called glycosylation. Glycosylation is a process by which sugar molecules (oligosaccharides) are attached to proteins and fats. Oligosaccharides are made up of many sugar molecules that are attached to one another in a stepwise process forming a complex chain. Glycosylation modifies proteins so they can perform a wider variety of functions. The enzyme produced from the ALG6 gene transfers a simple sugar called glucose to the growing oligosaccharide. Once the correct number of sugar molecules are linked together, the oligosaccharide is attached to a protein or fat.
At least 20 mutations in the ALG6 gene have been found to cause ALG6-congenital disorder of glycosylation (ALG6-CDG, also known as congenital disorder of glycosylation type Ic). This condition typically leads to developmental delay, vision problems, seizures, and other signs and symptoms. Mutations in the ALG6 gene result in the production of an abnormal enzyme with reduced or no activity. A common mutation replaces the protein building block (amino acid) alanine with the amino acid valine at position 333 in the enzyme. This mutation, written as Ala333Val or A333V, results in an enzyme with reduced activity. Without a properly functioning enzyme, glycosylation cannot proceed normally, and oligosaccharides are incomplete. As a result, glycosylation is reduced or absent. The wide variety of signs and symptoms in ALG6-CDG are likely due to impaired glycosylation of proteins and fats that are needed for normal function in many organs and tissues, including the brain, eyes, and hormone-producing (endocrine) system.
- asparagine-linked glycosylation 6 homolog (S. cerevisiae, alpha-1,3-glucosyltransferase)
- asparagine-linked glycosylation 6 homolog (yeast, alpha-1,3-glucosyltransferase)
- asparagine-linked glycosylation 6, alpha-1,3-glucosyltransferase homolog
- asparagine-linked glycosylation protein 6 homolog
- dol-P-Glc:Man(9)GlcNAc(2)-PP-Dol alpha-1,3-glucosyltransferase
- dolichyl-P-Glc:Man(9)GlcNAc(2)-PP-dolichol alpha- 1->3-glucosyltransferase
- dolichyl-P-Glc:Man9GlcNAc2-PP-dolichyl glucosyltransferase
- dolichyl pyrophosphate Man9GlcNAc2 alpha-1,3-glucosyltransferase
- dolichyl pyrophosphate Man9GlcNAc2 alpha-1,3-glucosyltransferase precursor
- Man(9)GlcNAc(2)-PP-Dol alpha-1,3-glucosyltransferase