Reactivity comparison of iron(II) reductant with type 1 copper(II) in native and type 2 copper-depleted Rhus vernicifera laccase

Robert A. Holwerda, Haesun Kang Baek, R. Max Wynn, David B. Knaff

Research output: Contribution to journalArticle

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Abstract

Rate constants and activation parameters are compared for the reductions of native and type 2 copper-depleted (T2D) Rhus vernicifera laccase type 1 Cu(II) by hydroxyethylferrocene, Fe(CN)64- and Fe(EDTA)2-. Oxidation of Fe(CN)64- (k(25°C)=1.45 · 102 M-1 · s-1, pH 7, I = 0.5 M) by T2D laccase blue copper is an order of magnitude faster than the corresponding native enzyme rate, and a type 2 Cu(II)-Fe(CN)64- interaction is shown to be responsible for complex kinetic behavior in the reduction of native laccase. Activation parameters (ΔH, ΔS) confirm the presence of a large conformational rearrangement barrier in the electron transfer pathway to laccase type 1 Cu(II), as compared with other blue copper proteins. A systematic compensation pattern between ΔH and ΔS in laccase reductions by Fe(II) redox agents suggests a common mechanism, with considerable flexibility in activation requirements, dependent upon the hydrophilicity of the electron donor.

Original languageEnglish (US)
Pages (from-to)112-116
Number of pages5
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume791
Issue number1
DOIs
StatePublished - Nov 23 1984

Fingerprint

Rhus
Laccase
Reducing Agents
Copper
Iron
Chemical activation
Electrons
Hydrophilicity
Hydrophobic and Hydrophilic Interactions
Edetic Acid
Oxidation-Reduction
Rate constants
Oxidation
Kinetics
Enzymes
Proteins

Keywords

  • (R vernicifera)
  • Electron transfer rate
  • Hydroxyethyl ferrocene
  • Laccase reduction

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology
  • Structural Biology

Cite this

Reactivity comparison of iron(II) reductant with type 1 copper(II) in native and type 2 copper-depleted Rhus vernicifera laccase. / Holwerda, Robert A.; Baek, Haesun Kang; Wynn, R. Max; Knaff, David B.

In: Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular, Vol. 791, No. 1, 23.11.1984, p. 112-116.

Research output: Contribution to journalArticle

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T1 - Reactivity comparison of iron(II) reductant with type 1 copper(II) in native and type 2 copper-depleted Rhus vernicifera laccase

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AU - Baek, Haesun Kang

AU - Wynn, R. Max

AU - Knaff, David B.

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N2 - Rate constants and activation parameters are compared for the reductions of native and type 2 copper-depleted (T2D) Rhus vernicifera laccase type 1 Cu(II) by hydroxyethylferrocene, Fe(CN)64- and Fe(EDTA)2-. Oxidation of Fe(CN)64- (k(25°C)=1.45 · 102 M-1 · s-1, pH 7, I = 0.5 M) by T2D laccase blue copper is an order of magnitude faster than the corresponding native enzyme rate, and a type 2 Cu(II)-Fe(CN)64- interaction is shown to be responsible for complex kinetic behavior in the reduction of native laccase. Activation parameters (ΔH‡, ΔS‡) confirm the presence of a large conformational rearrangement barrier in the electron transfer pathway to laccase type 1 Cu(II), as compared with other blue copper proteins. A systematic compensation pattern between ΔH‡ and ΔS‡ in laccase reductions by Fe(II) redox agents suggests a common mechanism, with considerable flexibility in activation requirements, dependent upon the hydrophilicity of the electron donor.

AB - Rate constants and activation parameters are compared for the reductions of native and type 2 copper-depleted (T2D) Rhus vernicifera laccase type 1 Cu(II) by hydroxyethylferrocene, Fe(CN)64- and Fe(EDTA)2-. Oxidation of Fe(CN)64- (k(25°C)=1.45 · 102 M-1 · s-1, pH 7, I = 0.5 M) by T2D laccase blue copper is an order of magnitude faster than the corresponding native enzyme rate, and a type 2 Cu(II)-Fe(CN)64- interaction is shown to be responsible for complex kinetic behavior in the reduction of native laccase. Activation parameters (ΔH‡, ΔS‡) confirm the presence of a large conformational rearrangement barrier in the electron transfer pathway to laccase type 1 Cu(II), as compared with other blue copper proteins. A systematic compensation pattern between ΔH‡ and ΔS‡ in laccase reductions by Fe(II) redox agents suggests a common mechanism, with considerable flexibility in activation requirements, dependent upon the hydrophilicity of the electron donor.

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