Contribution of Peroxidases in Host-Defense, Diseases and Cellular Functions

1. Peroxidase and related oxidase studies In 2000, a book entitled “The peroxidase multigene family of enzymes” (1) updated the peroxidase field and summarized the proceedings of the 2nd International Peroxidases Meeting held in Chiemsee and organized by Drs. Petro Petrides and William Nauseef. However since that time, several advances in the peroxidase field have occurred. Recent work has uncovered novel biochemistry, new gene families, and knock-out animals have been used to address important and unanswered questions. We convene now in Kyoto peroxidase scientists from around the world to discuss ongoing studies and share new insights into the biology of this important protein family. Myeloperoxidase (MPO): The organizing principle of the first peroxidase meeting was an interest in myeloperoxidase, the family member expressed in exclusively in cells of a neutrophilic or monocytic lineage. As neutrophils are the dominant cellular component of the human innate immune system and the oxygen-dependent antimicrobial system of neutrophils is the most efficient defense against microbes, MPO has a central place in neutrophil microbicidal action. Unique among the animal peroxidase family, MPO catalyzes the two electron oxidation of chloride ion in the presence of hydrogen peroxide to generate hypochlorous acid, a potent antimicrobial agent. The MPO-hydrogen peroxide-chloride system is responsible for microbicidal activity against a wide range of organisms and has served as the paradigm for neutrophil oxidative killing of bacteria. Dysfunction of host-defense due to MPO-deficiency in human: