Active site models for galactose oxidase containing two different phenol groups

Masayasu Taki; Hideyuki Kumei; Shigenori Nagatomo; Teizo Kitagawa; Shinobu Itoh; Shunichi Fukuzumi

doi:10.1016/S0020-1693(99)00579-4

Active site models for galactose oxidase containing two different phenol groups

Masayasu Taki, Hideyuki Kumei, Shigenori Nagatomo, Teizo Kitagawa, Shinobu Itoh, Shunichi Fukuzumi

Department of Chemistry & Nanoscience

Research output: Contribution to journal › Article › peer-review

42 Scopus citations

Abstract

Model complexes of the active site of galactose oxidase (GAO) have been developed using a new ligand carrying two different phenol groups, N-[(2-hydroxy-3-methylthio-5-tert-butylphenyl)methyl].N-[(2-hydroxy-3,5-di-te rt-butylphenyl)methyl].2-(2-pyridyl)ethylamine (L1H₂). Deprotonated ligand L1^2- forms a dimeric Cu(II) complex, [Cu(II)₂(L1^2-)₂], in the solid state, the structure of which has been determined by X-ray crystallographic analysis. The dimeric Cu(II)-diphenolate complex can be converted into the monomeric complex, [Cu(II)(L1^2-)(X)] (X = py, AcO, and PhCH₂OH), in solution by adding exogenous ligands such as pyridine (py), acetate (AcO^-), or benzyl alcohol (PhCH₂OH). The structure and physicochemical properties (UV-Vis, ESR, redox potential) of [Cu(II)(L1^2-)(X)] have been explored as a model for the resting state of the enzyme. One-electron oxidation of [Cu(II)(L1^2-)(py)] and [Zn(II)(L1^2-)(py)] by (NH₄)₂[Ce(IV)CNO₃)₆] (CAN) yielded the corresponding phenoxyl radical/phenolate complexes, Cu(II)(LI(·)^-) and Zn(II)(L1(·)^-), respectively, which have also been characterized by UV-Vis, resonance Raman, and ESR. The structure, physicochemical properties and reactivities of the diphenolate and phenoxyl radical/phenolate complexes of L1H₂ are compared to those of the corresponding monophenolate and monophenoxyl radical complexes in order to obtain further insight into the role of Tyr 495 in the native enzyme. (C) 2000 Elsevier Science S.A.

Original language	English
Pages (from-to)	622-632
Number of pages	11
Journal	Inorganica Chimica Acta
Volume	300-302
DOIs	https://doi.org/10.1016/S0020-1693(99)00579-4
State	Published - 30 Apr 2000

Bibliographical note

Funding Information:
The present study was financially supported in part by a Grant-in-Aid for Scientific Research on Priority Areas (Molecular Biometallics: 10129218 and 11116219; Electrochemistry of Ordered Interface: 10131242 and 11118244; Creation of Delocalized Conjugated Electronic System: 10146232) from the Ministry of Education, Science, Sports, and Culture of Japan and by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists (no. 02410). We also thank Professor Yasushi Kai and his co-workers, particularly, Ms Eiko Mochizuki of Osaka University, for their assistance in the X-ray measurements.

Keywords

Cofactor
Copper complexes
Galactose oxidase
Phenoxyl radical
Zinc complexes

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10.1016/S0020-1693(99)00579-4

Cite this

@article{2ccaf25cb38945e5964d5be00ca0cd7f,

title = "Active site models for galactose oxidase containing two different phenol groups",

abstract = "Model complexes of the active site of galactose oxidase (GAO) have been developed using a new ligand carrying two different phenol groups, N-[(2-hydroxy-3-methylthio-5-tert-butylphenyl)methyl].N-[(2-hydroxy-3,5-di-te rt-butylphenyl)methyl].2-(2-pyridyl)ethylamine (L1H2). Deprotonated ligand L12- forms a dimeric Cu(II) complex, [Cu(II)2(L12-)2], in the solid state, the structure of which has been determined by X-ray crystallographic analysis. The dimeric Cu(II)-diphenolate complex can be converted into the monomeric complex, [Cu(II)(L12-)(X)] (X = py, AcO, and PhCH2OH), in solution by adding exogenous ligands such as pyridine (py), acetate (AcO-), or benzyl alcohol (PhCH2OH). The structure and physicochemical properties (UV-Vis, ESR, redox potential) of [Cu(II)(L12-)(X)] have been explored as a model for the resting state of the enzyme. One-electron oxidation of [Cu(II)(L12-)(py)] and [Zn(II)(L12-)(py)] by (NH4)2[Ce(IV)CNO3)6] (CAN) yielded the corresponding phenoxyl radical/phenolate complexes, Cu(II)(LI(·)-) and Zn(II)(L1(·)-), respectively, which have also been characterized by UV-Vis, resonance Raman, and ESR. The structure, physicochemical properties and reactivities of the diphenolate and phenoxyl radical/phenolate complexes of L1H2 are compared to those of the corresponding monophenolate and monophenoxyl radical complexes in order to obtain further insight into the role of Tyr 495 in the native enzyme. (C) 2000 Elsevier Science S.A.",

keywords = "Cofactor, Copper complexes, Galactose oxidase, Phenoxyl radical, Zinc complexes",

author = "Masayasu Taki and Hideyuki Kumei and Shigenori Nagatomo and Teizo Kitagawa and Shinobu Itoh and Shunichi Fukuzumi",

note = "Funding Information: The present study was financially supported in part by a Grant-in-Aid for Scientific Research on Priority Areas (Molecular Biometallics: 10129218 and 11116219; Electrochemistry of Ordered Interface: 10131242 and 11118244; Creation of Delocalized Conjugated Electronic System: 10146232) from the Ministry of Education, Science, Sports, and Culture of Japan and by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists (no. 02410). We also thank Professor Yasushi Kai and his co-workers, particularly, Ms Eiko Mochizuki of Osaka University, for their assistance in the X-ray measurements.",

year = "2000",

month = apr,

day = "30",

doi = "10.1016/S0020-1693(99)00579-4",

language = "English",

volume = "300-302",

pages = "622--632",

journal = "Inorganica Chimica Acta",

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TY - JOUR

T1 - Active site models for galactose oxidase containing two different phenol groups

AU - Taki, Masayasu

AU - Kumei, Hideyuki

AU - Nagatomo, Shigenori

AU - Kitagawa, Teizo

AU - Itoh, Shinobu

AU - Fukuzumi, Shunichi

N1 - Funding Information: The present study was financially supported in part by a Grant-in-Aid for Scientific Research on Priority Areas (Molecular Biometallics: 10129218 and 11116219; Electrochemistry of Ordered Interface: 10131242 and 11118244; Creation of Delocalized Conjugated Electronic System: 10146232) from the Ministry of Education, Science, Sports, and Culture of Japan and by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists (no. 02410). We also thank Professor Yasushi Kai and his co-workers, particularly, Ms Eiko Mochizuki of Osaka University, for their assistance in the X-ray measurements.

PY - 2000/4/30

Y1 - 2000/4/30

N2 - Model complexes of the active site of galactose oxidase (GAO) have been developed using a new ligand carrying two different phenol groups, N-[(2-hydroxy-3-methylthio-5-tert-butylphenyl)methyl].N-[(2-hydroxy-3,5-di-te rt-butylphenyl)methyl].2-(2-pyridyl)ethylamine (L1H2). Deprotonated ligand L12- forms a dimeric Cu(II) complex, [Cu(II)2(L12-)2], in the solid state, the structure of which has been determined by X-ray crystallographic analysis. The dimeric Cu(II)-diphenolate complex can be converted into the monomeric complex, [Cu(II)(L12-)(X)] (X = py, AcO, and PhCH2OH), in solution by adding exogenous ligands such as pyridine (py), acetate (AcO-), or benzyl alcohol (PhCH2OH). The structure and physicochemical properties (UV-Vis, ESR, redox potential) of [Cu(II)(L12-)(X)] have been explored as a model for the resting state of the enzyme. One-electron oxidation of [Cu(II)(L12-)(py)] and [Zn(II)(L12-)(py)] by (NH4)2[Ce(IV)CNO3)6] (CAN) yielded the corresponding phenoxyl radical/phenolate complexes, Cu(II)(LI(·)-) and Zn(II)(L1(·)-), respectively, which have also been characterized by UV-Vis, resonance Raman, and ESR. The structure, physicochemical properties and reactivities of the diphenolate and phenoxyl radical/phenolate complexes of L1H2 are compared to those of the corresponding monophenolate and monophenoxyl radical complexes in order to obtain further insight into the role of Tyr 495 in the native enzyme. (C) 2000 Elsevier Science S.A.

AB - Model complexes of the active site of galactose oxidase (GAO) have been developed using a new ligand carrying two different phenol groups, N-[(2-hydroxy-3-methylthio-5-tert-butylphenyl)methyl].N-[(2-hydroxy-3,5-di-te rt-butylphenyl)methyl].2-(2-pyridyl)ethylamine (L1H2). Deprotonated ligand L12- forms a dimeric Cu(II) complex, [Cu(II)2(L12-)2], in the solid state, the structure of which has been determined by X-ray crystallographic analysis. The dimeric Cu(II)-diphenolate complex can be converted into the monomeric complex, [Cu(II)(L12-)(X)] (X = py, AcO, and PhCH2OH), in solution by adding exogenous ligands such as pyridine (py), acetate (AcO-), or benzyl alcohol (PhCH2OH). The structure and physicochemical properties (UV-Vis, ESR, redox potential) of [Cu(II)(L12-)(X)] have been explored as a model for the resting state of the enzyme. One-electron oxidation of [Cu(II)(L12-)(py)] and [Zn(II)(L12-)(py)] by (NH4)2[Ce(IV)CNO3)6] (CAN) yielded the corresponding phenoxyl radical/phenolate complexes, Cu(II)(LI(·)-) and Zn(II)(L1(·)-), respectively, which have also been characterized by UV-Vis, resonance Raman, and ESR. The structure, physicochemical properties and reactivities of the diphenolate and phenoxyl radical/phenolate complexes of L1H2 are compared to those of the corresponding monophenolate and monophenoxyl radical complexes in order to obtain further insight into the role of Tyr 495 in the native enzyme. (C) 2000 Elsevier Science S.A.

KW - Cofactor

KW - Copper complexes

KW - Galactose oxidase

KW - Phenoxyl radical

KW - Zinc complexes

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U2 - 10.1016/S0020-1693(99)00579-4

DO - 10.1016/S0020-1693(99)00579-4

M3 - Article

AN - SCOPUS:0034732486

SN - 0020-1693

VL - 300-302

SP - 622

EP - 632

JO - Inorganica Chimica Acta

JF - Inorganica Chimica Acta

ER -

Active site models for galactose oxidase containing two different phenol groups

Abstract

Bibliographical note

Keywords

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