1IQX

CRYSTAL STRUCTURE OF COBALT-SUBSTITUTED AMINE OXIDASE FROM ARTHROBACTER GLOBIFORMIS

Summary for 1IQX

• Entry DOI: 10.2210/pdb1iqx/pdb
• Related: 1AV4 1AVK 1AVL 1IQY
• Descriptor: CO(II)-SUBSTITUTED AMINE OXIDASE, COBALT (II) ION (3 entities in total)
• Functional Keywords: oxidoreductase, copper, amine oxidase, arthrobacter globiformis, quinone cofactor, tpq, cobalt, co(ii)
• Biological source: Arthrobacter globiformis
• Total number of polymer chains: 2
• Total formula weight: 141623.35

Authors

Kishishita, S.,Okajima, T.,Mure, M.,Kim, M.,Yamaguchi, H.,Hirota, S.,Suzuki, S.,Kuroda, S.,Tanizawa, K. (deposition date: 2001-08-27, release date: 2003-02-04, Last modification date: 2024-04-03)

Primary citation

Kishishita, S.,Okajima, T.,Kim, M.,Yamaguchi, H.,Hirota, S.,Suzuki, S.,Kuroda, S.,Tanizawa, K.,Mure, M.
Role of Copper Ion in Bacterial Copper Amine Oxidase: Spectroscopic and Crystallographic Studies of Metal-Substituted Enzymes
J.AM.CHEM.SOC., 125:1041-1055, 2003

PubMed Abstract: 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).

PubMed: 12537504
DOI: 10.1021/ja017899k

Experimental method

X-RAY DIFFRACTION (2 Å)