Galactose-1-phosphate Uridylyltransferase Deficiency - Cause

Cause

Lactose is a disaccharide consisting of glucose and galactose. After the ingestion of lactose, most commonly from breast milk for an infant or cow milk, the enzyme lactase hydrolyzes the sugar into its monosaccharide constituents, glucose and galactose. In the first step of galactose metabolism, galactose is converted to galactose 1-phosphate (Gal-1-P) by the enzyme galactokinase. Gal-1-P is converted to uridine diphosphate (UDP) galactose by the enzyme galactose-1-phosphate uridylyltransferase, with UDP-glucose acting as a UDP donor. UDP-galactose can then be converted to lactose, by the enzyme lactose synthase, or to UDP-glucose by UDP galactose epimerase.

In classic galactosemia, galactose-1-phosphate uridylyltransferase activity is reduced or absent, leading to an accumulation of galactose and Gal-1-P.