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PDBsum entry 2uya
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References listed in PDB file
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Key reference
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Title
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The identity of the active site of oxalate decarboxylase and the importance of the stability of active-Site lid conformations.
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Authors
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V.J.Just,
M.R.Burrell,
L.Bowater,
I.Mcrobbie,
C.E.Stevenson,
D.M.Lawson,
S.Bornemann.
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Ref.
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Biochem J, 2007,
407,
397-406.
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PubMed id
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Abstract
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Oxalate decarboxylase (EC 4.1.1.2) catalyses the conversion of oxalate into
carbon dioxide and formate. It requires manganese and, uniquely, dioxygen for
catalysis. It forms a homohexamer and each subunit contains two similar, but
distinct, manganese sites termed sites 1 and 2. There is kinetic evidence that
only site 1 is catalytically active and that site 2 is purely structural.
However, the kinetics of enzymes with mutations in site 2 are often ambiguous
and all mutant kinetics have been interpreted without structural information.
Nine new site-directed mutants have been generated and four mutant crystal
structures have now been solved. Most mutants targeted (i) the flexibility
(T165P), (ii) favoured conformation (S161A, S164A, D297A or H299A) or (iii)
presence (Delta162-163 or Delta162-164) of a lid associated with site 1. The
kinetics of these mutants were consistent with only site 1 being catalytically
active. This was particularly striking with D297A and H299A because they
disrupted hydrogen bonds between the lid and a neighbouring subunit only when in
the open conformation and were distant from site 2. These observations also
provided the first evidence that the flexibility and stability of lid
conformations are important in catalysis. The deletion of the lid to mimic the
plant oxalate oxidase led to a loss of decarboxylase activity, but only a slight
elevation in the oxalate oxidase side reaction, implying other changes are
required to afford a reaction specificity switch. The four mutant crystal
structures (R92A, E162A, Delta162-163 and S161A) strongly support the hypothesis
that site 2 is purely structural.
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