Download Xanthine Oxidase (XO)

Xanthine Oxidase (XO)
學生:李威聰
指導老師:李惠春
Introduction
Function
Structure
Property
Gout
Function
In purine degradation, it oxidizes
hypoxanthine successively to
xanthine and then to uric acid
Stucture
 Homodimer
 Each monomer has three domains
N-terminal domain (residues 1~165):
two Fe/S cofactors
FAD-binding domain (residues
226~553)
The third domain (residues
590~1332): one molybdenum
Fe/S convert XDH (xanthine
dehydrogenase) to XO
FAD reduction of O2
Molybdenum oxidative hydroxylation
of purine
Property
Ubiquitous among species and within the
various tissues
Normally it exists in the liver and
jejunum
determination of serum xanthine
oxidase level serves as a sensitive
indicator of acute liver damage
In individuals, 90% is XDH form, and
10% is XO form
 XDHXO (oxidation of sulfhydryl or
proteolysis)
Difference between XO & XDH:
XO XH+H2O+O2X=O+H2O2
XDH XH+H2O+NAD+X=O+NADH
Other names: xanthine oxidoreductase,
hypoxanthine oxidase, hypoxanthinexanthine oxidase
Gout
A form of arthritis caused by excess
uric acid (hyperuricemia)
Complication can result death
Cause: heredity, diet, fatness, sex,
excessive exercise, drug, alcohol, and
some diseases
Drug can decrease patients’ pains and
prevent it
an attack of acute gout: colchicine
lower conc. of uric acid: allopurinol