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ALG6 gene
URL of this page: https://medlineplus.gov/genetics/gene/alg6/

ALG6 gene

ALG6 alpha-1,3-glucosyltransferase

Normal Function

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.

Health Conditions Related to Genetic Changes

ALG6-congenital disorder of glycosylation

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.

More About This Health Condition

Other Names for This Gene

  • 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 pyrophosphate Man9GlcNAc2 alpha-1,3-glucosyltransferase
  • dolichyl pyrophosphate Man9GlcNAc2 alpha-1,3-glucosyltransferase precursor
  • dolichyl-P-Glc:Man(9)GlcNAc(2)-PP-dolichol alpha- 1->3-glucosyltransferase
  • dolichyl-P-Glc:Man9GlcNAc2-PP-dolichyl glucosyltransferase
  • dolichyl-P-Glc:Man9GlcNAc2-PP-dolichylglucosyltransferase
  • Man(9)GlcNAc(2)-PP-Dol alpha-1,3-glucosyltransferase

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Grunewald S, Imbach T, Huijben K, Rubio-Gozalbo ME, Verrips A, de Klerk JB, Stroink H, de Rijk-van Andel JF, Van Hove JL, Wendel U, Matthijs G, Hennet T, Jaeken J, Wevers RA. Clinical and biochemical characteristics of congenital disorder of glycosylation type Ic, the first recognized endoplasmic reticulum defect in N-glycan synthesis. Ann Neurol. 2000 Jun;47(6):776-81. Citation on PubMed
  • Imbach T, Burda P, Kuhnert P, Wevers RA, Aebi M, Berger EG, Hennet T. A mutation in the human ortholog of the Saccharomyces cerevisiae ALG6 gene causes carbohydrate-deficient glycoprotein syndrome type-Ic. Proc Natl Acad Sci U S A. 1999 Jun 8;96(12):6982-7. doi: 10.1073/pnas.96.12.6982. Citation on PubMed or Free article on PubMed Central
  • Sparks SE, Krasnewich DM. Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview. 2005 Aug 15 [updated 2017 Jan 12]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from http://www.ncbi.nlm.nih.gov/books/NBK1332/ Citation on PubMed
  • Westphal V, Xiao M, Kwok PY, Freeze HH. Identification of a frequent variant in ALG6, the cause of Congenital Disorder of Glycosylation-Ic. Hum Mutat. 2003 Nov;22(5):420-1. doi: 10.1002/humu.9195. Citation on PubMed

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