| Structural highlights
Function
UGE2_ARATH Catalyzes the interconversion between UDP-glucose and UDP-galactose (PubMed:16644739, PubMed:19754426, Ref.6). Cooperates with UGE3 in pollen development and with UGE4 in cell wall carbohydrate biosynthesis and growth (PubMed:17496119).[1] [2] [3] [REFERENCE:6]
Publication Abstract from PubMed
L-Arabinose (L-Ara) is a plant-specific sugar found in cell wall polysaccharides, proteoglycans, glycoproteins, and small glycoconjugates, which play physiologically important roles in cell proliferation and other essential cellular processes. L-Ara is synthesized as UDP-L-arabinose (UDP-L-Ara) from UDP-xylose (UDP-Xyl) by UDP-Xyl 4-epimerases (UXEs), a type of de novo synthesis of L-Ara unique to plants. In Arabidopsis, the Golgi-localized UXE AtMUR4 is the main contributor to UDP-L-Ara synthesis. However, cytosolic bifunctional UDP-glucose 4-epimerases (UGEs) with UXE activity, AtUGE1, and AtUGE3 also catalyze this reaction. For the present study, we first examined the physiological importance of bifunctional UGEs in Arabidopsis. The uge1 and uge3 mutants enhanced the dwarf phenotype of mur4 and further reduced the L-Ara content in cell walls, suggesting that bifunctional UGEs contribute to UDP-L-Ara synthesis. Through the introduction of point mutations exchanging corresponding amino acid residues between AtUGE1 with high UXE activity and AtUGE2 with low UXE activity, two mutations that increase relative UXE activity of AtUGE2 were identified. The crystal structures of AtUGE2 in complex forms with NAD(+) and NAD(+)/UDP revealed that the UDP-binding domain of AtUGE2 has a more closed conformation and smaller sugar-binding site than bacterial and mammalian UGEs, suggesting that plant UGEs have the appropriate size and shape for binding UDP-Xyl and UDP-L-Ara to exhibit UXE activity. The presented results suggest that the capacity for cytosolic synthesis of UDP-L-Ara was acquired by the small sugar-binding site and several mutations of UGEs, enabling diversified utilization of L-Ara in seed plants.
Cytosolic UDP-L-arabinose synthesis by bifunctional UDP-glucose 4-epimerases in Arabidopsis.,Umezawa A, Matsumoto M, Handa H, Nakazawa K, Miyagawa M, Seifert GJ, Takahashi D, Fushinobu S, Kotake T Plant J. 2024 Apr 28. doi: 10.1111/tpj.16779. PMID:38678521[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Barber C, Rösti J, Rawat A, Findlay K, Roberts K, Seifert GJ. Distinct properties of the five UDP-D-glucose/UDP-D-galactose 4-epimerase isoforms of Arabidopsis thaliana. J Biol Chem. 2006 Jun 23;281(25):17276-17285. PMID:16644739 doi:10.1074/jbc.M512727200
- ↑ Rösti J, Barton CJ, Albrecht S, Dupree P, Pauly M, Findlay K, Roberts K, Seifert GJ. UDP-glucose 4-epimerase isoforms UGE2 and UGE4 cooperate in providing UDP-galactose for cell wall biosynthesis and growth of Arabidopsis thaliana. Plant Cell. 2007 May;19(5):1565-79. PMID:17496119 doi:10.1105/tpc.106.049619
- ↑ Kotake T, Takata R, Verma R, Takaba M, Yamaguchi D, Orita T, Kaneko S, Matsuoka K, Koyama T, Reiter WD, Tsumuraya Y. Bifunctional cytosolic UDP-glucose 4-epimerases catalyse the interconversion between UDP-D-xylose and UDP-L-arabinose in plants. Biochem J. 2009 Nov 11;424(2):169-77. PMID:19754426 doi:10.1042/BJ20091025
- ↑ Umezawa A, Matsumoto M, Handa H, Nakazawa K, Miyagawa M, Seifert GJ, Takahashi D, Fushinobu S, Kotake T. Cytosolic UDP-L-arabinose synthesis by bifunctional UDP-glucose 4-epimerases in Arabidopsis. Plant J. 2024 Apr 28. PMID:38678521 doi:10.1111/tpj.16779
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