In enzymology, an UTP—hexose-1-phosphate uridylyltransferase (EC 2.7.7.10) is an enzyme that catalyzes the chemical reaction

UTP + alpha-D-galactose 1-phosphate diphosphate + UDP-galactose

Thus, the two substrates of this enzyme are UTP and alpha-D-galactose 1-phosphate, whereas its two products are diphosphate and UDP-galactose.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is UTP:alpha-D-hexose-1-phosphate uridylyltransferase. Other names in common use include galactose-1-phosphate uridylyltransferase, galactose 1-phosphate uridylyltransferase, alpha-D-galactose 1-phosphate uridylyltransferase, galactose 1-phosphate uridyltransferase, UDPgalactose pyrophosphorylase, uridine diphosphate galactose pyrophosphorylase, and uridine diphosphogalactose pyrophosphorylase. This enzyme participates in galactose metabolism and nucleotide sugars metabolism.

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1GUP, 1GUQ, and 1HXP.

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