TY - JOUR
T1 - The oxidized (3,3) state of manganese catalase. Comparison of enzymes from Thermus thermophilus and Lactobacillus plantarum
AU - Whittaker, Mei M.
AU - Barynin, Vladimir V.
AU - Antonyuk, Svetlana V.
AU - Whittaker, James W.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1999/7/13
Y1 - 1999/7/13
N2 - Manganese catalases contain a binuclear manganese cluster that catalyzes the redox dismutation of hydrogen peroxide, interconverting between dimanganese(II) [(2,2)] and dimanganese(III) [(3,3)] oxidation states during turnover. We have investigated the oxidized (3,3) states of the homologous enzymes from Thermus thermophilus and Lactobacillus plantarum using a combination of optical absorption, CD, MCD, and EPR spectroscopies as sensitive probes of the electronic structure and protein environment for the active site metal clusters. Comparison of results for these two enzymes allows the essential features of the active sites to be recognized and the differences identified. For both enzymes, preparations having the highest catalytic activity have diamagnetic ground states, consistent with the bis- μ-bridging dimanganese core structure that has been defined crystallographically. Oxidative damage and exogenous ligand binding perturb the core structure of LPC, converting the enzyme to a distinct form in which the cluster becomes paramagnetic as a result of altered exchange coupling mediated by the bridging ligands. The TTC cluster does not exhibit this sensitivity to ligand binding, implying a different reactivity for the bridges in that enzyme. A mechanism is proposed involving distinct coordination modes for peroxide substrate in each of the two half-reactions for enzyme turnover.
AB - Manganese catalases contain a binuclear manganese cluster that catalyzes the redox dismutation of hydrogen peroxide, interconverting between dimanganese(II) [(2,2)] and dimanganese(III) [(3,3)] oxidation states during turnover. We have investigated the oxidized (3,3) states of the homologous enzymes from Thermus thermophilus and Lactobacillus plantarum using a combination of optical absorption, CD, MCD, and EPR spectroscopies as sensitive probes of the electronic structure and protein environment for the active site metal clusters. Comparison of results for these two enzymes allows the essential features of the active sites to be recognized and the differences identified. For both enzymes, preparations having the highest catalytic activity have diamagnetic ground states, consistent with the bis- μ-bridging dimanganese core structure that has been defined crystallographically. Oxidative damage and exogenous ligand binding perturb the core structure of LPC, converting the enzyme to a distinct form in which the cluster becomes paramagnetic as a result of altered exchange coupling mediated by the bridging ligands. The TTC cluster does not exhibit this sensitivity to ligand binding, implying a different reactivity for the bridges in that enzyme. A mechanism is proposed involving distinct coordination modes for peroxide substrate in each of the two half-reactions for enzyme turnover.
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U2 - 10.1021/bi990499d
DO - 10.1021/bi990499d
M3 - Article
C2 - 10413487
AN - SCOPUS:0033551493
SN - 0006-2960
VL - 38
SP - 9126
EP - 9136
JO - Biochemistry
JF - Biochemistry
IS - 28
ER -