|Gene:||xdh||Accession Number: G-12642 (MetaCyc)|
Species: Haloferax volcanii
The native apparent molecular mass was determined by gel filtration chromatography [Johnsen09].
This enzyme was shown to catalyze the first reaction in the oxidative xylose degradation pathway of the halophilic archaeon Haloferax volcanii (see pathway xylose degradation III). It showed 59% amino acid sequence identity to a functionally characterized xylose dehydrogenase from Haloarcula marismortui and 56% identity to an ortholog in Halorubrum lacusprofundi, but was only 11% identical to the bacterial NAD+-dependent xylose dehydrogenase from Caulobacter crescentus CB15 [Johnsen09, Johnsen04].
The enzyme was induced by growth of cells on α-D-xylopyranose (D-xylose). Native enzyme was purified from cell extracts. Recombinant, His-tagged enzyme was expressed in Escherichia coli, but it was catalytically inactive due to misfolding after expression in a nonhalophilic organism. The enzyme was reactivated by denaturation in urea followed by refolding in the presence of salts and substrates, and was purified and characterized [Johnsen09].
The subunit apparent molecular mass was determined by SDS-PAGE to be 55.5 kDa. The discrepancy with the calculated molecular mass of 42.3 kDa is common in halophilic proteins [Johnsen09].
The genome of this organism is composed of a main chromosome of 2.848 Mb, three smaller chromosomes (pHV4, pHV3 and pHV1) and a plasmid pHV2 [Hartman10]. This gene is located on pHV3.
|Map Position: [30,784 -> 31,956]|
Molecular Weight of Polypeptide: 42.307 kD (from nucleotide sequence), 55.5 kD (experimental) [Johnsen09 ]
Molecular Weight of Multimer: 165.0 kD (experimental) [Johnsen09]
Enzymatic reaction of: D-xylose dehydrogenase
Synonyms: xylose dehydrogenase
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 in which it was curated.
This reaction is reversible.
This enzyme was highly specific for α-D-xylopyranose as substrate. D-glucose showed a 130-fold lower catalytic efficiency. L-arabinose, D-arabinose, D-ribose, D-mannose and L-mannose were not significantly oxidized. The enzyme was also specific for NADP+ as cofactor and no activity was found with NAD+ [Johnsen09].
Drew98: Drew KN, Zajicek J, Bondo G, Bose B, Serianni AS (1998). "13C-labeled aldopentoses: detection and quantitation of cyclic and acyclic forms by heteronuclear 1D and 2D NMR spectroscopy." Carbohydrate Research 307(3-4);199-209.
Hartman10: Hartman AL, Norais C, Badger JH, Delmas S, Haldenby S, Madupu R, Robinson J, Khouri H, Ren Q, Lowe TM, Maupin-Furlow J, Pohlschroder M, Daniels C, Pfeiffer F, Allers T, Eisen JA (2010). "The complete genome sequence of Haloferax volcanii DS2, a model archaeon." PLoS One 5(3);e9605. PMID: 20333302
Johnsen09: Johnsen U, Dambeck M, Zaiss H, Fuhrer T, Soppa J, Sauer U, Schonheit P (2009). "D-xylose degradation pathway in the halophilic archaeon Haloferax volcanii." J Biol Chem 284(40);27290-303. PMID: 19584053
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