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Molecular characterization of the membrane‐bound quinol peroxidase functionally connected to the respiratory chain
Author(s) -
Yamada Hiroyuki,
Takashima Eizo,
Konishi Kiyoshi
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2006.05637.x
Subject(s) - peroxidase , heme , biochemistry , respiratory chain , cytochrome c , cytochrome , biology , ubiquinol , cytochrome c peroxidase , chemistry , enzyme , microbiology and biotechnology , coenzyme q – cytochrome c reductase , mitochondrion
Here, we report for the first time quinol peroxidase (QPO), an enzyme that uses ubiquinol‐1 as an electron donor for the reduction of H 2 O 2 to water. We purified QPO to > 90% purity from the membrane fraction of Actinobacillus actinomycetemcomitans . QPO is a 53.6‐kDa protein that contains three heme c molecules. The qpo gene was predicted to encode a putative bacterial cytochrome c peroxidase with N‐terminal extensions containing an additional potential heme c ‐binding motif. Although qpo has high sequence homology to bacterial cytochrome c peroxidases, QPO did not catalyze peroxidation in the presence of horse heart cytochrome c . In addition, the cytoplasmic membrane of A. actinomycetemcomitans had apparent QPO‐dependent peroxidase activity in the presence of NADH or succinate, which are substrates for the respiratory chain. Based on these findings, we present a new mechanism for the scavenging of reactive oxygen species in which quinol in the respiratory chain is consumed.