TY - JOUR
T1 - Kinetic studies on the formation and decomposition of compounds II and III
T2 - Reactions of lignin peroxidase with H2O2
AU - Cai, Denying
AU - Tien, Ming
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1992/6/5
Y1 - 1992/6/5
N2 - The present study characterizes the serial reactions of H2O2 with compounds I and II of lignin peroxidase isozyme H1. These two reactions constitute part of the pathway leading to formation of the oxy complex (compound III) from the ferric enzyme. Compounds II and III are the only complexes observed; no compound III* is observed. Compound III* is proposed to be an adduct of compound III with H2O2 formed from the complexation of compound III with H2O2 (Wariishi, H., and Gold, M. H. (1990) J. Biol. Chem. 265, 2070-2077). We provide evidence that demonstrates that the spectral data, on which the formation of compound III* is based, are merely an artifact caused by enzyme instability and, therefore, rule out the existence of compound III*. The reactions of compounds II and III with H2O2 are pH-dependent, similar to that observed for reactions of compounds I and II with the reducing substrate veratryl alcohol. The spontaneous decay of the compound III of lignin peroxidase results in the reduction of ferric cytochrome c. The reduction is inhibited by Superoxide dismutase, indicating that superoxide is released during the decay. Therefore, the lignin peroxidase compound III decays to the ferric enzyme through the dissociation of Superoxide. This mechanism is identical with that observed with oxymyoglobin and oxyhemoglobin but different from that for horseradish peroxidase. Compound III is capable of reacting with small molecules, such as tetranitromethane (a Superoxide scavenger) and fluoride (a ligand for the ferric enzyme), resulting in ferric enzyme and fluoride complex formation, respectively.
AB - The present study characterizes the serial reactions of H2O2 with compounds I and II of lignin peroxidase isozyme H1. These two reactions constitute part of the pathway leading to formation of the oxy complex (compound III) from the ferric enzyme. Compounds II and III are the only complexes observed; no compound III* is observed. Compound III* is proposed to be an adduct of compound III with H2O2 formed from the complexation of compound III with H2O2 (Wariishi, H., and Gold, M. H. (1990) J. Biol. Chem. 265, 2070-2077). We provide evidence that demonstrates that the spectral data, on which the formation of compound III* is based, are merely an artifact caused by enzyme instability and, therefore, rule out the existence of compound III*. The reactions of compounds II and III with H2O2 are pH-dependent, similar to that observed for reactions of compounds I and II with the reducing substrate veratryl alcohol. The spontaneous decay of the compound III of lignin peroxidase results in the reduction of ferric cytochrome c. The reduction is inhibited by Superoxide dismutase, indicating that superoxide is released during the decay. Therefore, the lignin peroxidase compound III decays to the ferric enzyme through the dissociation of Superoxide. This mechanism is identical with that observed with oxymyoglobin and oxyhemoglobin but different from that for horseradish peroxidase. Compound III is capable of reacting with small molecules, such as tetranitromethane (a Superoxide scavenger) and fluoride (a ligand for the ferric enzyme), resulting in ferric enzyme and fluoride complex formation, respectively.
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M3 - Article
C2 - 1317857
AN - SCOPUS:0026781048
SN - 0021-9258
VL - 267
SP - 11149
EP - 11155
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 16
ER -