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Title
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Structure and assembly of protocatechuate 3,4-dioxygenase.
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Authors
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D.H.Ohlendorf,
J.D.Lipscomb,
P.C.Weber.
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Ref.
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Nature, 1988,
336,
403-405.
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PubMed id
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Abstract
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Dioxygenases catalyse the cleavage of molecular oxygen with subsequent
incorporation of both oxygen atoms into organic substrates. Some of the
best-studied dioxygenases have been isolated from bacteria where they catalyse
the critical ring-opening step in the biodegradation of aromatic compounds.
These bacterial enzymes generally contain nonheme ferric iron as the sole
cofactor. Protocatechuate 3,4-dioxygenase (3,4-PCD) was one of the first such
enzymes recognized and catalyses the intradiol cleavage of protocatechuic acid
by oxygen to produce beta-carboxy-cis,cis-muconic acid. Previous studies have
shown that the 3,4-PCD found in Pseudomonas aeruginosa is an oligomer with a
relative molecular mass (Mr) of 587,000 (587K) containing 12 copies each of
alpha (22.3K) and beta (26.6K) subunits. The X-ray structure determination of
3,4-PCD reveals the catalytic iron environment required for oxygenolytic
cleavage of aromatic rings and also provides a novel holoenzyme assembly with
cubic 23(T) symmetry and first examples of mixed beta-barrel domains.
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