UDP-glucuronate decarboxylase 1 (UXS1)

Abstract

UDP-glucuronate decarboxylase/UDP-xylose synthase (UXS1) catalyzes the conversion of UDP-glucuronic acid to UDP-xylose by a decarboxylation reaction (Fig. 127.1a). At least in animals, it is assumed that this is the only enzyme catalyzing this reaction and, in contrast to plants (Kotake et al. 2004), probably no salvage pathway for xylose exists (Bakker et al. 2009). UXS1 is unique among the enzymes involved in nucleotide sugar biosynthesis in that it is localized within the lumen of the secretory pathway (Kearns et al. 1993; Hwang and Horvitz 2002; Moriarity et al. 2002). In fungi (Bar-Peled et al. 2001) and plants (Harper and Bar-Peled 2002; Kobayashi et al. 2002), however, either the enzyme is found in the cytoplasm (fungi) or different enzymes exist that are localized in the cytoplasm and the ER or Golgi (plants).