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PDBsum entry 1u5u
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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 structure of coral allene oxide synthase reveals a catalase adapted for metabolism of a fatty acid hydroperoxide.
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Authors
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M.L.Oldham,
A.R.Brash,
M.E.Newcomer.
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Ref.
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Proc Natl Acad Sci U S A, 2005,
102,
297-302.
[DOI no: ]
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PubMed id
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Abstract
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8R-Lipoxygenase and allene oxide synthase (AOS) are parts of a naturally
occurring fusion protein from the coral Plexaura homomalla. AOS catalyses the
production of an unstable epoxide (an allene oxide) from the fatty acid
hydroperoxide generated by the lipoxygenase activity. Here, we report the
structure of the AOS domain and its striking structural homology to catalase.
Whereas nominal sequence identity between the enzymes had been previously
described, the extent of structural homology observed was not anticipated, given
that this enzyme activity had been exclusively associated with the P450
superfamily, and conservation of a catalase fold without catalase activity is
unprecedented. Whereas the heme environment is largely conserved, the AOS heme
is planar and the distal histidine is flanked by two hydrogen-bonding residues.
These critical differences likely facilitate the switch from a catalatic
activity to that of a fatty acid hydroperoxidase.
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Figure 1.
Fig. 1. Comparison of allene oxide biosynthesis in coral
and plants. The conversion of allene oxide to clavulone remains
unproven.
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Figure 3.
Fig. 3. Comparison of AOS and catalase. (a) Superimposition
of AOS (green; heme is red) with HEC (gray; heme is blue). The
catalase N-terminal threading arm and wrapping domains are
indicated. (b) Superposition of the heme environments of AOS
(green carbons) and catalase (gray carbons). Dashed lines
indicating active-site hydrogen bonds are black (AOS) and pink
(HEC), respectively.
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