ABSTRACT
This chapter considers the interaction of all mentioned oxygen species with substrates, cellular components, and cells. It shows that oxygen radicals are also able to activate some enzymes, to promote iron transport, and to stimulate other important processes. One of the most important questions is the identification of a genuine active species among various oxygen radicals participating in biological processes. The mechanism of the interaction of oxygen radicals with proteins depends on their structure and functions. The role of oxygen radicals in physiological and pathological processes is now far from being completely understood and depends on the ability of oxygen radicals to interact with substrates, drugs, proteins, lipids, enzymes, DNA, and other cellular compounds. The superoxide ion is able not only to oxidize, but also to bind catechols to biological polymers. An example of superoxide-mediated reactions of thiols is the interaction of thiols with catechols. Melanins are polymers derived from enzymatic oxidation of catecholamines.
