|Gene:||GAE4||Accession Number: AT2G45310 (MetaCyc)|
Synonyms: UGlcAE1, UDP-D-GlcA 4-epimerase, UDP-D-glucuronate 4-epimerase, UDP-D-galacturonic acid 4-epimerase, UDP-D-galacturonate 4-epimerase, UDP-D-GalA 4-epimerase
Species: Arabidopsis thaliana col
Subunit composition of
UDP-D-glucuronic acid 4-epimerase = [GAE4]2
subunit of UDP-GlcA 4-epimerase = GAE4
This Arabidopsis thaliana enzyme (UGlcAE1) catalyzes the epimerization of UDP-α-D-glucuronate (UDP-GlcA) to UDP-α-D-galacturonate (UDP-GalA). The dimeric protein is encoded by the UGlcAE1 gene. Expression of the full-length gene in E.colifails to produce an active enzyme. It was postulated that the hydrophobic putative N-terminal transmembrane domain results in un- or misfolding of the protein in inclusion bodies [Gu04]. A partially purified recombinant UGlcAE1Δ1-64, lacking the transmembrane domain, however, could be expressed in E.coli and was shown to have a UDP-GlcA 4-epimerase catalytic activity [Gu04]. The reaction is reversible, but favours the formation of UDP-GalA over UDP-GlcA with an equilibrium constant of approximately 1.9. The enzyme does not require NAD+ or metal ions for activity, and maintains maximum activity in the presence of EDTA. The enzyme has a broad pH range (6.4 to 8.2) centered around 7.4-7.6. Activity is completely abolished at pH values lower than 4 and higher than 9.5 in phosphate buffer [Gu04]. The temperature range is also broad with enzyme activity between 25?C and 55?C with maximal activity between 30?C and 42?C. UDP-glucose and UDP-galactose had no inhibitory effect while UDP-xylose, UDP-arabinose and UDP were strong inhibitors.
Molecular Weight of Polypeptide: 43.5 kD (from nucleotide sequence)
Molecular Weight of Multimer: 88 kD (experimental) [Gu04]
Unification Links: Entrez:AAT06796 , ModBase:O22141 , PhylomeDB:O22141 , Pride:O22141 , Protein Model Portal:O22141 , SMR:O22141 , String:3702.AT2G45310.1-P , Swiss-Model:O22141 , TAIR:AT2G45310 , UniProt:O22141
Enzymatic reaction of: UDP-D-glucuronic acid 4-epimerase
EC Number: 18.104.22.168
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.
This reaction is reversible.
T(opt): 36 °C [Gu04]
pH(opt): 7.5 [Gu04]
Gu04: Gu X, Bar-Peled M (2004). "The biosynthesis of UDP-galacturonic acid in plants. Functional cloning and characterization of Arabidopsis UDP-D-glucuronic acid 4-epimerase." Plant Physiol 136(4);4256-64. PMID: 15563616
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