TY - JOUR
T1 - Reactivity comparison of iron(II) reductant with type 1 copper(II) in native and type 2 copper-depleted Rhus vernicifera laccase
AU - Holwerda, Robert A.
AU - Baek, Haesun Kang
AU - Wynn, R. Max
AU - Knaff, David B.
N1 - Funding Information:
We thank the Robert A. Welch Foundation for support of this research through grants D-735 (R.A.H.) and D-710 (D.B.K.).
PY - 1984/11/23
Y1 - 1984/11/23
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.
KW - (R vernicifera)
KW - Electron transfer rate
KW - Hydroxyethyl ferrocene
KW - Laccase reduction
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U2 - 10.1016/0167-4838(84)90288-7
DO - 10.1016/0167-4838(84)90288-7
M3 - Article
AN - SCOPUS:48549114959
SN - 0167-4838
VL - 791
SP - 112
EP - 116
JO - Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
JF - Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
IS - 1
ER -