Skip Navigation
Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed January 2008

What is the official name of the GALK1 gene?

The official name of this gene is “galactokinase 1.”

GALK1 is the gene's official symbol. The GALK1 gene is also known by other names, listed below.

What is the normal function of the GALK1 gene?

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.

How are changes in the GALK1 gene related to health conditions?

galactosemia - caused by mutations in the GALK1 gene

More than 20 mutations in the GALK1 gene have been identified in people with a form of galactosemia called type II or galactokinase deficiency. 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. Clouding of the lens, which is called a cataract, is a hallmark of galactosemia type II.

Where is the GALK1 gene located?

Cytogenetic Location: 17q24

Molecular Location on chromosome 17: base pairs 75,757,936 to 75,765,198

The GALK1 gene is located on the long (q) arm of chromosome 17 at position 24.

The GALK1 gene is located on the long (q) arm of chromosome 17 at position 24.

More precisely, the GALK1 gene is located from base pair 75,757,936 to base pair 75,765,198 on chromosome 17.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about GALK1?

You and your healthcare professional may find the following resources about GALK1 helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the GALK1 gene or gene products?

  • ATP:D-galactose 1-phosphotransferase
  • galactokinase
  • GALK
  • GK1

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding GALK1?

acids ; ATP ; cataract ; deficiency ; D-galactose ; enzyme ; galactose ; gene ; glucose ; glycolipid ; molecule ; phosphate ; protein ; simple sugar

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Holden HM, Rayment I, Thoden JB. Structure and function of enzymes of the Leloir pathway for galactose metabolism. J Biol Chem. 2003 Nov 7;278(45):43885-8. Epub 2003 Aug 15. Review. (
  • 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. (
  • Leslie ND. Insights into the pathogenesis of galactosemia. Annu Rev Nutr. 2003;23:59-80. Epub 2003 Apr 9. Review. (
  • NCBI Gene (
  • Novelli G, Reichardt JK. Molecular basis of disorders of human galactose metabolism: past, present, and future. Mol Genet Metab. 2000 Sep-Oct;71(1-2):62-5. Review. (
  • Sangiuolo F, Magnani M, Stambolian D, Novelli G. Biochemical characterization of two GALK1 mutations in patients with galactokinase deficiency. Hum Mutat. 2004 Apr;23(4):396. (
  • 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. (
  • Timson DJ, Reece RJ. Functional analysis of disease-causing mutations in human galactokinase. Eur J Biochem. 2003 Apr;270(8):1767-74. (
  • Timson DJ, Reece RJ. Sugar recognition by human galactokinase. BMC Biochem. 2003 Nov 4;4:16. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: January 2008
Published: July 27, 2015