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PDBsum entry 2wd4
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Oxidoreductase
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PDB id
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2wd4
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References listed in PDB file
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Key reference
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Title
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Evidence for heme oxygenase activity in a heme peroxidase.
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Authors
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S.K.Badyal,
G.Eaton,
S.Mistry,
Z.Pipirou,
J.Basran,
C.L.Metcalfe,
A.Gumiero,
S.Handa,
P.C.Moody,
E.L.Raven.
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Ref.
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Biochemistry, 2009,
48,
4738-4746.
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PubMed id
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Abstract
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The heme peroxidase and heme oxygenase enzymes share a common heme prosthetic
group but catalyze fundamentally different reactions, the first being
H(2)O(2)-dependent oxidation of substrate using an oxidized Compound I
intermediate, and the second O(2)-dependent degradation of heme. It has been
proposed that these enzymes utilize a common reaction intermediate, a ferric
hydroperoxide species, that sits at a crossroads in the mechanism and beyond
which there are two mutually exclusive mechanistic pathways. Here, we present
evidence to support this proposal in a heme peroxidase. Hence, we describe
kinetic data for a variant of ascorbate peroxidase (W41A) which reacts slowly
with tert-butyl hydroperoxide and does not form the usual peroxidase Compound I
intermediate; instead, structural data show that a product is formed in which
the heme has been cleaved at the alpha-meso position, analogous to the heme
oxygenase mechanism. We interpret this to mean that the Compound I (peroxidase)
pathway is shut down, so that instead the reaction intermediate diverts through
the alternative (heme oxygenase) route. A mechanism for formation of the product
is proposed and discussed in the light of what is known about the heme oxygenase
reaction mechanism.
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