1rov
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(New page: 200px<br /><applet load="1rov" size="450" color="white" frame="true" align="right" spinBox="true" caption="1rov, resolution 2.00Å" /> '''Lipoxygenase-3 Treat...)
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Revision as of 23:38, 20 November 2007
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Lipoxygenase-3 Treated with Cumene Hydroperoxide
Overview
Lipoxygenase catalysis depends in a critical fashion on the redox, properties of a unique mononuclear non-heme iron cofactor. The isolated, enzyme contains predominantly, if not exclusively, iron(II), but the, catalytically active form of the enzyme has iron(III). The activating, oxidation of the iron takes place in a reaction with the hydroperoxide, product of the catalyzed reaction. In a second peroxide-dependent process, lipoxygenases are also inactivated. To examine the redox, activation/inactivation dichotomy in lipoxygenase chemistry, the, interaction between lipoxygenase-1 (and -3) and cumene hydroperoxide was, investigated. Cumene hydroperoxide was a reversible inhibitor of the, reaction catalyzed by lipoxygenase-1 under standard assay conditions at, high substrate concentrations. Reconciliation of the data with the, currently held kinetic mechanism requires simultaneous binding of, substrate and peroxide. The enzyme also was both oxidized and largely, inactivated in a reaction with the peroxide in the absence of substrate., The consequences of this reaction for the enzyme included the, hydroxylation at C beta of two amino acid side chains in the vicinity of, the cofactor, Trp and Leu. The modifications were identified by mass, spectrometry and X-ray crystallography. The peroxide-induced oxidation of, iron was also accompanied by a subtle rearrangement in the coordination, sphere of the non-heme iron atom. Since the enzyme retains catalytic, activity, albeit diminished, after treatment with cumene hydroperoxide, the structure of the iron site may reflect the catalytically relevant form, of the cofactor.
About this Structure
1ROV is a Single protein structure of sequence from Glycine max with FE as ligand. Active as Lipoxygenase, with EC number 1.13.11.12 Full crystallographic information is available from OCA.
Reference
Interaction between non-heme iron of lipoxygenases and cumene hydroperoxide: basis for enzyme activation, inactivation, and inhibition., Vahedi-Faridi A, Brault PA, Shah P, Kim YW, Dunham WR, Funk MO Jr, J Am Chem Soc. 2004 Feb 25;126(7):2006-15. PMID:14971933
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