The GALK1 gene provides instructions for making an enzyme called galactokinase 1. This enzyme enables the body to process a simple sugar called galactose, which is present in small amounts in many foods. Galactose is primarily part of a larger sugar called lactose, which is found in all dairy products and many baby formulas.
Galactokinase 1 is responsible for one step in a chemical process that converts galactose into other molecules that can be used by the body. Specifically, this enzyme modifies galactose to create a similar molecule called galactose-1-phosphate. A series of additional steps converts galactose-1-phosphate to another simple sugar called glucose, which is the main energy source for most cells. Galactose-1-phosphate can also be converted to a form that is used to build galactose-containing proteins and fats. These modified proteins and fats play critical roles in chemical signaling, building cellular structures, transporting molecules, and producing energy.
Health Conditions Related to Genetic Changes
More than 30 mutations in the GALK1 gene have been identified in people with a form of galactosemia called type II or galactokinase deficiency. Affected infants develop clouding of the lens of the eye (cataracts) but otherwise experience few of the long-term complications associated with classic galactosemia. Most of these mutations change single protein building blocks (amino acids) in galactokinase 1. A few mutations delete a small amount of genetic material from the GALK1 gene, resulting in an unstable or inactive version of this enzyme.
A shortage of functional galactokinase 1 prevents cells from processing galactose obtained from the diet. As a result, galactose and a related sugar called galactitol can build up, particularly in cells that make up the lens of the eye. An accumulation of these substances damages the lens, causing it to become cloudy and leading to blurred vision.More About This Health Condition
Other Names for This Gene
- ATP:D-galactose 1-phosphotransferase
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
- Berry GT. Classic Galactosemia and Clinical Variant Galactosemia. 2000 Feb 4 [updated 2020 Jul 2]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1518/ Citation on PubMed
- Holden HM, Thoden JB, Timson DJ, Reece RJ. Galactokinase: structure, function and role in type II galactosemia. Cell Mol Life Sci. 2004 Oct;61(19-20):2471-84. Review. Citation on PubMed
- Thoden JB, Holden HM. The molecular architecture of human N-acetylgalactosamine kinase. J Biol Chem. 2005 Sep 23;280(38):32784-91. Epub 2005 Jul 8. Citation on PubMed
- Timson DJ, Reece RJ. Functional analysis of disease-causing mutations in human galactokinase. Eur J Biochem. 2003 Apr;270(8):1767-74. Citation on PubMed
- Timson DJ, Reece RJ. Sugar recognition by human galactokinase. BMC Biochem. 2003 Nov 4;4:16. Citation on PubMed or Free article on PubMed Central
- Timson DJ. The molecular basis of galactosemia - Past, present and future. Gene. 2016 Sep 10;589(2):133-41. doi: 10.1016/j.gene.2015.06.077. Epub 2015 Jul 2. Review. Citation on PubMed