MetaCyc Enzyme: L-xylulose reductase

Gene: lxrA Accession Number: G-12471 (MetaCyc)

Synonyms: JGI177736

Species: Aspergillus niger

Subunit composition of L-xylulose reductase = [LxrA]8
         L-xylulose reductase subunit = LxrA

This enzyme is considered to be the true L-arabinose-inducible, NADPH-dependent L-xylulose reductase encoded by gene lxrA in Aspergillus niger ([Mojzita10] and reviewed in [Seiboth11]).

L-Xylulose reductase was purified from cell-free extracts of mycelium from Aspergillus niger. The native relative molecular mass was determined by gel filtration chromatography [Witteveen94].

Recombinant enzyme was expressed in Saccharomyces cerevisiae, purified as a His-tagged protein, and characterized [Mojzita10].
The relative molecular mass of the L-xylulose reductase subunit was determined by SDS-PAGE [Witteveen94].

Molecular Weight of Polypeptide: 32 kD (experimental) [Witteveen94 ]

Molecular Weight of Multimer: 250 kD (experimental) [Witteveen94]

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Created 23-May-2007 by Fulcher CA , SRI International
Revised 18-Jan-2011 by Fulcher CA , SRI International

Enzymatic reaction of: L-xylulose reductase

Synonyms: xylitol dehydrogenase, xylitol:NADP+ 4-oxidoreductase (L-xylulose-forming)

EC Number:

xylitol + NADP+ <=> L-xylulose + NADPH + H+

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. [Seiboth07]

In Pathways: superpathway of pentose and pentitol degradation , L-arabinose degradation II

The pH optimum of the reductase (forward) reaction was described as around 6.5 and broad. The enzyme was highly specific for L-xylulose in the forward direction and for xylitol in the reverse (oxidative) direction. A low level of activity was found with the substrates D-xylulose, D-erythrose and dihydroxyacetone in the forward direction, and with D-sorbitol in the reverse direction. It was also highly specific for NADPH and no activity was found with NADH. [Witteveen94]

Product inhibition was observed. The enzyme showed competitive inhibition by NADPH relative to NADP+ and vice versa. Xylitol inhibited at very high concentration. L-xylulose inhibited, but the assay accuracy was too low to determine the inhibition type. [Witteveen94]

Inhibitors (Competitive): NADPH [Witteveen94] , NADP+ [Witteveen94]

Inhibitors (Unknown Mechanism): L-xylulose [Witteveen94]

Kinetic Parameters:

Km (μM)

pH(opt): 6.5 [Witteveen94]


Mojzita10: Mojzita D, Vuoristo K, Koivistoinen OM, Penttila M, Richard P (2010). "The 'true' L-xylulose reductase of filamentous fungi identified in Aspergillus niger." FEBS Lett 584(16);3540-4. PMID: 20654618

Seiboth07: Seiboth B, Gamauf C, Pail M, Hartl L, Kubicek CP (2007). "The D-xylose reductase of Hypocrea jecorina is the major aldose reductase in pentose and D-galactose catabolism and necessary for beta-galactosidase and cellulase induction by lactose." Mol Microbiol 66(4);890-900. PMID: 17924946

Seiboth11: Seiboth B, Metz B (2011). "Fungal arabinan and L: -arabinose metabolism." Appl Microbiol Biotechnol. PMID: 21212945

Witteveen94: Witteveen C. F. B., Weber F., Busink R., Visser J. (1994). "Isolation and characterization of two xylitol dehydrogenases from Aspergillus niger." Microbiology 140, 1679-1685.

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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