tailieunhanh - Báo cáo khoa học: Molecular characterization of the membrane-bound quinol peroxidase functionally connected to the respiratory chain

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 ofActino-bacillus actinomycetemcomitans. QPO is a protein that contains three heme c molecules. Theqpogene was predicted to encode a putative bacterial cytochromec peroxidase with N-terminal extensions containing an additional potential hemec-binding motif. | ỊFEBS Journal Molecular characterization of the membrane-bound quinol peroxidase functionally connected to the respiratory chain Hiroyuki Yamada Eizo Takashima and Kiyoshi Konishi Department of Microbiology Schoolof Life Dentistry at Tokyo Nippon DentalUniversity Tokyo Japan Keywords respiratory chain quinone peroxidase oxidative stress Actinobacillus actinomycetemcomitans Correspondence E. Takashima Department of Microbiology Schoolof Life Dentistry at Tokyo Nippon DentalUniversity 1-9-20 Fujimi Chiyoda-ku Tokyo 102-8159 Japan Fax Tel 81 3 3261 8763 E-mail eizo26@ Received 2 October 2006 revised 30 November 2006 accepted 6 December 2006 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 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. doi Actinobacillus actinomycetemcomitans is a facultative anaerobic CO2-requiring Gram-negative human pathogen in the gamma subdivision of the Proteobacteria 1 . As a member of the family Pasteurellaceae it is related to the well-studied genera Haemophilus and Pasteurella. A. actinomycetemcomitans has been associated with a .

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