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.