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Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
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MetaCyc Enzyme: xanthine dehydrogenase

Species: [Clostridium] purinilyticum

Subunit composition of xanthine dehydrogenase = [xanthine dehydrogenase α subunit]4[xanthine dehydrogenase β subunit]4[xanthine dehydrogenase γ subunit]4

Summary:
xanthine dehydrogenase is a seleno-molybdo-iron-sulfur flavoprotein that belongs to the family of molybdenum hydroxylases. These enzymes contain FAD, a molybdenum cofactor, and at least one Fe/S center. In addition, these proteins have an additional sulfur or selenium atom, which is required for activity. The enzyme lacks selenocysteine, and contains selenium in a relatively unstable form, and only rarely contains the full complement of 2 mol Se per mol of enzyme [Meyer00, Self00].

The enzyme from [Clostridium] purinilyticum has been purified 349-fold to homogeneity [Self00]. It is a large complex composed of three different subunits, possibly containing 4 copies of each. Unlike similar enzymes from related organisms, the enzyme from [Clostridium] purinilyticum was not sensitive to oxygen, and was stable in the presence of air.

Hydroxylation of the purine ring occurs at the 8-position. The enzyme accepts several purine compouds as substrates, but the Km value of other substrates is much higher than that for xanthine (4.5 μM), suggesting that the later is probably the preferred substrate in vivo [Self00].

Molecular Weight: 529 kD (experimental) [Self00 ]

Gene-Reaction Schematic: ?

Credits:
Created 30-Mar-2007 by Caspi R , SRI International


Enzymatic reaction of: xanthine dehydrogenase

EC Number: 1.17.1.4

xanthine + NAD+ + H2O <=> urate + NADH + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

This reaction is reversible.

Alternative Substrates for xanthine: allopurinol [Self00 ] , 2-hydroxypurine [Self00 ] , hypoxanthine [Self00 ] , 1-methylxanthine [Self00 ]

In Pathways: purine nucleobases degradation I (anaerobic)

Cofactors or Prosthetic Groups: Se0 [Self00], FAD [Self00], an iron-sulfur cluster [Self00], MoO2-molybdopterin cofactor [Self00]

Inhibitors (Other): hydrogen cyanide [Self00]

Kinetic Parameters:

Substrate
Km (μM)
Citations
xanthine
4.5
[Self00]


Subunit of xanthine dehydrogenase: xanthine dehydrogenase α subunit

Molecular Weight: 80 kD (experimental) [Self00]


Subunit of xanthine dehydrogenase: xanthine dehydrogenase β subunit

Molecular Weight: 35 kD (experimental) [Self00]


Subunit of xanthine dehydrogenase: xanthine dehydrogenase γ subunit

Molecular Weight: 16 kD (experimental) [Self00]


References

Meyer00: Meyer O, Gremer L, Ferner R, Ferner M, Dobbek H, Gnida M, Meyer-Klaucke W, Huber R (2000). "The role of Se, Mo and Fe in the structure and function of carbon monoxide dehydrogenase." Biol Chem 381(9-10);865-76. PMID: 11076018

Self00: Self WT, Stadtman TC (2000). "Selenium-dependent metabolism of purines: A selenium-dependent purine hydroxylase and xanthine dehydrogenase were purified from Clostridium purinolyticum and characterized." Proc Natl Acad Sci U S A 97(13);7208-13. PMID: 10860985


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Thu Dec 18, 2014, biocyc13.