Xanthine oxidoreductase: structure, distribution and physioloical role

The article presents an overview of the modern literature on the structure, distribution, biological and physiological role of xanthine oxidoreductase (XOR). XOR has been identified in all living organisms, from bacteria to humans. However, only in mammals it is presented in two forms, other species contain exclusively the XDH form. The enzyme is a homodimer with independent electron transfer in each monomer. XOR catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid in the final stage of purine metabolism and is widely distributed enzyme. The review highlights the forms of XOR and their role in the generation of reactive oxygen species (ROS), reactive nitrogen species (RNS) and synthesis of uric acid which are involved in many physiological processes. Uric acid shows antioxidant activity, and ROS and RNS play a role in innate immunity, in signaling, metabolism of xenobiotics, regulation of cellular redox potential and are also involved in mammogenesis and lactogenesis. Thus, in recent years significant progress has been made in understanding the biochemical and physiological nature of this enzyme system.