Galactosemia
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What is galactosemia?
Galactosemia is a disorder that affects how the body processes certain sugars (sugar metabolism). This condition results when the body is not able to process the sugar galactose, which is found in many foods. Galactose also exists as part of another sugar, lactose, found in all dairy products. Liver dysfunction, cataracts (clouding of the lens of the eye), speech problems, and mental impairment are characteristic of this condition if not treated.
How common is galactosemia?
Classic galactosemia is an inherited disorder that occurs in approximately 1 in 30,000 live births. The incidence of the Duarte variant, a mild type of galactosemia, is more common. This variant affects an estimated 1 in 16,000 live births.
What genes are related to galactosemia?
Mutations in the GALE, GALK1, and GALT genes cause galactosemia.
Most cases of galactosemia are categorized as classic, or type I, galactosemia and are caused by mutations in the GALT gene. This gene produces the enzyme galactose-1-phosphate uridyl-transferase, which is important in processing galactose. Mutations in the GALT gene cause two forms of type I galactosemia, classic and Duarte variant. Individuals with the classic type of galactosemia lack nearly all the enzyme activity necessary to metabolize galactose. Individuals with the Duarte variant have approximately 5 to 20 percent of the enzyme activity necessary to metabolize this sugar and often do not have signs or symptoms of galactosemia.
Galactosemia type II results from mutations in the GALK1 gene, which cause a shortage of the enzyme galactokinase. Galactosemia type III results from mutations in the GALE gene, which cause a shortage of the enzyme UDP-galactose-4-epimerase. Both of these enzymes also play a role in the proper metabolism of galactose.
How do people inherit galactosemia?
This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.
Source: National Institutes of Health
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Recent findings from Hallym University highlight research in galactosemia
2009 MAY 11 - (NewsRx.com) -- According to recent research from South Korea, "Galactosemia is caused by defects in the galactose metabolic pathway, which consists of three enzymes, including UDP-galactose-4-epimerase (GALE). We previously reported nine mutations in Korean patients with epimerase-deficiency galactosemia." "In order to determine the functional consequences of these mutations, we expressed wild-type and mutant GALE proteins in 293T cells. GALE(E165K) and GALE(W336X) proteins were unstable, had reduced half-life, formed aggregates and were partly degraded by the proteasome complex. When expressed in GALE-null ldlD cells GALE(E165K), GALE(R239W), GALE(G302D) and GALE(W336X) had no detectable enzyme activity, although substantial amounts of protein were detected in western blots. The relative activities of other mutants were lower than that of wild-type. In addition, unlike wild-type, GALE(R239W) and GALE(G302D) were not able to rescue galactose-sensitive cell proliferation when stably expressed in ldlD cells. The four inactive mutant proteins did not show defects in dimerization or affect the activity of other mutant alleles identified in patients," wrote Y.L. Bang and colleagues, Hallym University. The researchers concluded: "Our observations show that altered protein stability is due to misfolding and that loss or reduction of enzyme activity is responsible for the molecular defects underlying GALE-deficiency galactosemia." Bang and colleagues published their study in Febs Journal (Functional analysis of mutations in UDP-galactose-4-epimerase (GALE) associated with galactosemia in Korean patients using mammalian GALE-null cells. Febs Journal, 2009;276(7):1952-1961). For additional information, contact Y.H. Song, Hallym University, Ilsong Institute Life Science, 1605-4 Gwanyang Dong, Anyang 431060, Gyeonggi Do, South Korea. Publisher contact information for the Febs Journal is: Wiley-Blackwell Publishing, Inc., Commerce Place, 350 Main St., Malden 02148, MA, USA. Keywords: South Korea, Enzyme Research, Epimerase, Galactosemia, Genetics, Metabolic Disease, Hallym University. This article was prepared by Proteomics Weekly editors from staff and other reports. Copyright 2009, Proteomics Weekly via NewsRx.com.
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