Peroxidase-ROS interactions\

Reactive oxygen species (ROS), such as hydrogen peroxide and superoxide anion radical, have long been recognized as harmful by-products of oxidative metabolism. Under normal physiologic conditions, hydrogen peroxide and superoxide are detoxified by antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx). Heme peroxidases (eosinophil peroxidase (EPO), lactoperoxidase (LPO), myeloperoxidase (MPO), etc.) also consume ROS, but unlike scavenging enzymes, are sources of these species as well. In the present paper, we study a well-tested model of the peroxidase-oxidase (PO) reaction based on horseradish peroxidase (HRP) chemistry with regard to the production and consumption of hydrogen peroxide and superoxide. Our principal results are these: 1. PO reactions can transduce continuing infusions of hydrogen peroxide and superoxide into bounded dynamics. 2. Absent exogenous ROS input, and under conditions that retard hydrogen donor autoxidation, PO reactions can manifest low frequency bursting whereby pulses of ROS are produced at clinically significant intervals. The relevance of these results to the functional significance of fluctuating ROS concentrations in vivo, to neurodevelopmental and neurodegenerative disease and to episodic and progressive symptomatology is discussed.