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Title
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Structural analysis of urate oxidase in complex with its natural substrate inhibited by cyanide: mechanistic implications.
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Authors
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L.Gabison,
T.Prangé,
N.Colloc'h,
M.El Hajji,
B.Castro,
M.Chiadmi.
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Ref.
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Bmc Struct Biol, 2008,
8,
32-32.
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PubMed id
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Abstract
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BACKGROUND: Urate oxidase (EC 1.7.3.3 or UOX) catalyzes the conversion of uric
acid and gaseous molecular oxygen to 5-hydroxyisourate and hydrogen peroxide, in
the absence of cofactor or particular metal cation. The functional enzyme is a
homo-tetramer with four active sites located at dimeric interfaces. RESULTS: The
catalytic mechanism was investigated through a ternary complex formed between
the enzyme, uric acid, and cyanide that stabilizes an intermediate state of the
reaction. When uric acid is replaced by a competitive inhibitor, no complex with
cyanide is formed. CONCLUSION: The X-ray structure of this compulsory ternary
complex led to a number of mechanistic evidences that support a sequential
mechanism in which the two reagents, dioxygen and a water molecule, process
through a common site located 3.3 A above the mean plane of the ligand. This
site is built by the side chains of Asn 254, and Thr 57, two conserved residues
belonging to two different subunits of the homo-tetramer. The absence of a
ternary complex between the enzyme, a competitive inhibitor, and cyanide
suggests that cyanide inhibits the hydroxylation step of the reaction, after the
initial formation of a hydroperoxyde type intermediate.
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