GALT gene
The GALT gene provides instructions for making an enzyme necessary for processing galactose, a simple sugar found in dairy products and many baby formulas.
Normal Function
The GALT gene provides instructions for making an enzyme called galactose-1-phosphate uridylyltransferase. 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.
Galactose-1-phosphate uridylyltransferase is responsible for one step in a chemical process that breaks down galactose into other molecules that can be used by the body. Specifically, this enzyme converts a modified form of galactose (galactose-1-phosphate) to glucose, which is the main energy source for most cells. This chemical reaction also produces another form of galactose (UDP-galactose) that is used to build galactose-containing proteins and fats, which play critical roles in chemical signaling, building cellular structures, transporting molecules, and producing energy.
Health Conditions Related to Genetic Changes
Galactosemia
More than 300 mutations in the GALT gene have been identified in people with the classic form of galactosemia, a condition that causes life-threatening signs and symptoms beginning shortly after birth. Most of these mutations severely reduce or eliminate the activity of galactose-1-phosphate uridylyltransferase. A shortage of this enzyme prevents cells from processing galactose obtained from the diet, causing galactose-1-phosphate and related compounds to build up to toxic levels, which damages tissues and organs.
- Common Mutations: Most changes alter single amino acids. The most common mutation in white Europeans and North Americans replaces glutamine with arginine at position 188 (Gln188Arg or Q188R). A mutation occurring almost exclusively in people of African descent substitutes leucine for serine at position 135 (Ser135Leu or S135L).
- Duarte Variant: A mutation that replaces asparagine with aspartic acid at position 314 (Asn314Asp or N314D) results in a form of galactosemia with less serious complications. This variant reduces but does not eliminate enzyme activity, which retains 5 percent to 20 percent of its normal function.
Other Names for This Gene
- Gal-1-P uridylyltransferase
- Galactosephosphate Uridylyltransferase
- GALT_HUMAN
- UDP Galactose Pyrophosphorylase
- UTP-Hexose-1-Phosphate Uridylyltransferase
- UTP:alpha-D-hexose-1-phosphate uridylyltransferase