Journal
FEBS JOURNAL
Volume 274, Issue 3, Pages 853-866Publisher
BLACKWELL PUBLISHING
DOI: 10.1111/j.1742-4658.2006.05637.x
Keywords
respiratory chain; quinone; peroxidase; oxidative stress; Actinobacillus actinomycetemcomitans
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Here, we report for the first time quinol peroxidase (QPO), an enzyme that uses ubiquinol-1 as an electron donor for the reduction of H2O2 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.
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