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PDBsum entry 1sp8
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Oxidoreductase
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PDB id
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1sp8
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Contents |
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* Residue conservation analysis
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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 crystal structures of zea mays and arabidopsis 4-Hydroxyphenylpyruvate dioxygenase.
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Authors
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I.M.Fritze,
L.Linden,
J.Freigang,
G.Auerbach,
R.Huber,
S.Steinbacher.
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Ref.
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Plant Physiol, 2004,
134,
1388-1400.
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PubMed id
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Abstract
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The transformation of 4-hydroxyphenylpyruvate to homogentisate, catalyzed by
4-hydroxyphenylpyruvate dioxygenase (HPPD), plays an important role in degrading
aromatic amino acids. As the reaction product homogentisate serves as aromatic
precursor for prenylquinone synthesis in plants, the enzyme is an interesting
target for herbicides. In this study we report the first x-ray structures of the
plant HPPDs of Zea mays and Arabidopsis in their substrate-free form at 2.0 A
and 3.0 A resolution, respectively. Previous biochemical characterizations have
demonstrated that eukaryotic enzymes behave as homodimers in contrast to
prokaryotic HPPDs, which are homotetramers. Plant and bacterial enzymes share
the overall fold but use orthogonal surfaces for oligomerization. In addition,
comparison of both structures provides direct evidence that the C-terminal helix
gates substrate access to the active site around a nonheme ferrous iron center.
In the Z. mays HPPD structure this helix packs into the active site,
sequestering it completely from the solvent. In contrast, in the Arabidopsis
structure this helix tilted by about 60 degrees into the solvent and leaves the
active site fully accessible. By elucidating the structure of plant HPPD enzymes
we aim to provide a structural basis for the development of new herbicides.
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