5fli

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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Quercetin 2,4-dioxygenase (quercetinase) from Streptomyces uses nickel as the active-site cofactor to catalyze oxidative cleavage of the flavonol quercetin. How this unusual active-site metal supports catalysis and O2 activation is under debate. We present crystal structures of Ni-quercetinase in three different states, thus providing direct insight into how quercetin and O2 are activated at the Ni(2+) ion. The Ni(2+) ion is coordinated by three histidine residues and a glutamate residue (E(76) ) in all three states. Upon binding, quercetin replaces one water ligand at Ni and is stabilized by a short hydrogen bond through E(76) , the carboxylate group of which rotates by 90 degrees . This conformational change weakens the interaction between Ni and the remaining water ligand, thereby preparing a coordination site at Ni to bind O2 . O2 binds side-on to the Ni(2+) ion and is perpendicular to the C2-C3 and C3-C4 bonds of quercetin, which are cleaved in the following reaction steps.
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Biotin is an essential vitamin in plants and mammals, functioning as the carbon dioxide carrier within central lipid metabolism. Bacterial pimeloyl-CoA synthetase (BioW) acts as a highly specific substrate-selection gate, ensuring the integrity of the carbon chain in biotin synthesis. BioW catalyzes the condensation of pimelic acid (C7 dicarboxylic acid) with CoASH in an ATP-dependent manner to form pimeloyl-CoA, the first dedicated biotin building block. Multiple structures of Bacillus subtilis BioW together capture all three substrates, as well as the intermediate pimeloyl-adenylate and product pyrophosphate (PPi), indicating that the enzyme uses an internal ruler to select the correct dicarboxylic acid substrate. Both the catalytic mechanism and the surprising stability of the adenylate intermediate were rationalized through site-directed mutagenesis. Building on this understanding, BioW was engineered to synthesize high-value heptanoyl (C7) and octanoyl (C8) monocarboxylic acid-CoA and C8 dicarboxylic-CoA products, highlighting the enzyme's synthetic potential.
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Quercetin 2,4-Dioxygenase Activates Dioxygen in a Side-On O2 -Ni Complex.,Jeoung JH, Nianios D, Fetzner S, Dobbek H Angew Chem Int Ed Engl. 2016 Mar 1;55(10):3281-4. doi: 10.1002/anie.201510741., Epub 2016 Feb 5. PMID:26846734<ref>PMID:26846734</ref>
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Using the pimeloyl-CoA synthetase adenylation fold to synthesize fatty acid thioesters.,Wang M, Moynie L, Harrison PJ, Kelly V, Piper A, Naismith JH, Campopiano DJ Nat Chem Biol. 2017 Apr 17. doi: 10.1038/nchembio.2361. PMID:28414710<ref>PMID:28414710</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 07:42, 27 April 2017

enzyme-substrate complex of Ni-quercetinase

5fli, resolution 2.15Å

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