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| | {{STRUCTURE_1iqx| PDB=1iqx | SCENE= }} | | {{STRUCTURE_1iqx| PDB=1iqx | SCENE= }} |
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| - | '''CRYSTAL STRUCTURE OF COBALT-SUBSTITUTED AMINE OXIDASE FROM ARTHROBACTER GLOBIFORMIS'''
| + | ===CRYSTAL STRUCTURE OF COBALT-SUBSTITUTED AMINE OXIDASE FROM ARTHROBACTER GLOBIFORMIS=== |
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| - | ==Overview==
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| - | The role of the active site Cu(2+) of phenylethylamine oxidase from Arthrobacter globiformis (AGAO) has been studied by substitution with other divalent cations, where we were able to remove >99.5% of Cu(2+) from the active site. The enzymes reconstituted with Co(2+) and Ni(2+) (Co- and Ni-AGAO) exhibited 2.2 and 0.9% activities, respectively, of the original Cu(2+)-enzyme (Cu-AGAO), but their K(m) values for amine substrate and dioxygen were comparable. X-ray crystal structures of the Co- and Ni-AGAO were solved at 2.0-1.8 A resolution. These structures revealed changes in the metal coordination environment when compared to that of Cu-AGAO. However, the hydrogen-bonding network around the active site involving metal-coordinating and noncoordinating water molecules was preserved. Upon anaerobic mixing of the Cu-, Co-, and Ni-AGAO with amine substrate, the 480 nm absorption band characteristic of the oxidized form of the topaquinone cofactor (TPQ(ox)) disappeared rapidly (< 6 ms), yielding the aminoresorcinol form of the reduced cofactor (TPQ(amr)). In contrast to the substrate-reduced Cu-AGAO, the semiquinone radical (TPQ(sq)) was not detected in Co- and Ni-AGAO. Further, in the latter, TPQ(amr) reacted reversibly with the product aldehyde to form a species with a lambda(max) at around 350 nm that was assigned as the neutral form of the product Schiff base (TPQ(pim)). Introduction of dioxygen to the substrate-reduced Co- and Ni-AGAO resulted in the formation of a TPQ-related intermediate absorbing at around 360 nm, which was assigned to the neutral iminoquinone form of the 2e(-)-oxidized cofactor (TPQ(imq)) and which decayed concomitantly with the generation of TPQ(ox). The rate of TPQ(imq) formation and its subsequent decay in Co- and Ni-AGAO was slow when compared to those of the corresponding reactions in Cu-AGAO. The low catalytic activities of the metal-substituted enzymes are due to the impaired efficiencies of the oxidative half-reaction in the catalytic cycle of amine oxidation. On the basis of these results, we propose that the native Cu(2+) ion has essential roles such as catalyzing the electron transfer between TPQ(amr) and dioxygen, in part by providing a binding site for 1e(-)- and 2e(-)-reduced dioxygen species to be efficiently protonated and released and also preventing the back reaction between the product aldehyde and TPQ(amr). | + | The line below this paragraph, {{ABSTRACT_PUBMED_12537504}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 12537504 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_12537504}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Quinone cofactor]] | | [[Category: Quinone cofactor]] |
| | [[Category: Tpq]] | | [[Category: Tpq]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 20:18:10 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 13:50:09 2008'' |
Revision as of 10:50, 1 July 2008
Template:STRUCTURE 1iqx
CRYSTAL STRUCTURE OF COBALT-SUBSTITUTED AMINE OXIDASE FROM ARTHROBACTER GLOBIFORMIS
Template:ABSTRACT PUBMED 12537504
About this Structure
1IQX is a Single protein structure of sequence from Arthrobacter globiformis. Full crystallographic information is available from OCA.
Reference
Role of copper ion in bacterial copper amine oxidase: spectroscopic and crystallographic studies of metal-substituted enzymes., Kishishita S, Okajima T, Kim M, Yamaguchi H, Hirota S, Suzuki S, Kuroda S, Tanizawa K, Mure M, J Am Chem Soc. 2003 Jan 29;125(4):1041-55. PMID:12537504
Page seeded by OCA on Tue Jul 1 13:50:09 2008
