UDP-glucose 4-epimerase

n/an/an/an/anan/an/an/an/an/aThe enzyme UDP-glucose 4-epimerase (EC 5.1.3.2), also known as UDP-galactose 4-epimerase or GALE, is a homodimeric epimerase found in bacterial, fungal, plant, and mammalian cells.

This enzyme performs the final step in the Leloir pathway of galactose metabolism, catalyzing the reversible conversion of UDP-galactose to UDP-glucose.

[2] Additionally, human and some bacterial GALE isoforms reversibly catalyze the formation of UDP-N-acetylgalactosamine (UDP-GalNAc) from UDP-N-acetylglucosamine (UDP-GlcNAc) in the presence of NAD+, an initial step in glycoprotein or glycolipid synthesis.

[3] Dr. Luis Leloir deduced the role of GALE in galactose metabolism during his tenure at the Instituto de Investigaciones Bioquímicas del Fundación Campomar, initially terming the enzyme waldenase.

[1] Human and some bacterial GALE isoforms reversibly catalyze the conversion of UDP-GlcNAc to UDP-GalNAc through an identical mechanism, inverting the stereochemical configuration at the sugar's 4' hydroxyl group.

A family of glycosyltransferases known as UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosamine transferases (ppGaNTases) transfers GalNAc from UDP-GalNAc to glycoprotein serine and threonine residues.

[15] ppGaNTase-mediated glycosylation regulates protein sorting,[16][17][18][19][20] ligand signaling,[21][22][23] resistance to proteolytic attack,[24][25] and represents the first committed step in mucin biosynthesis.

[15] Human GALE deficiency or dysfunction results in Type III galactosemia, which may exist in a mild (peripheral) or more severe (generalized) form.