UDP-galactose-4-epimerase (GALE)

Abstract

UDP-galactose 4-epimerase (GALE; EC 5.1.3.2; UniProt: Q14376) catalyzes the interconversion of UDP-galactose and UDP-glucose (Fig. 128.1a). In the majority of eukaryotes studied to date, the enzyme is also able to interconvert UDP-N-acetylgalactosamine (UDP-GalNAc) and UDP-N-acetylglucosamine (UDP-GlcNAc) (Fig. 128.1b). The first of these reactions occurs as part of the Leloir pathway, which converts galactose into the glycolytic intermediate glucose-6-phosphate. Both reactions are important in the maintenance of UDP-monosaccharide pools and, consequently, in supplying raw materials for the glycosylation of proteins and lipids. The enzyme has attracted considerable research interest because mutations in the corresponding gene are associated with the genetic disease type III galactosemia (OMIN #230350). There is also some interest in using the enzyme as a biocatalyst to interconvert its substrates and related UDP-monosaccharides.