Oxidoreductase Inhibitors

Abstract

Chemical reactions that occur via the exchange of electrons are termed redox reactions. Normally the carbon atom changes its oxidation state in biochemical redox processes. As a general rule, derivatives with a significant number of directly bound hydrogen atoms are transformed into derivatives with a larger number of contacts to nitrogen, oxygen, and sulfur in oxidations. Because these bonds to the above-mentioned electronegative elements are usually associated with the introduction of polar functional groups, redox reactions exert a decisive influence on the physicochemical properties of the oxidized substances. For example, the water solubility is increased. This is of great importance for the elimination of xenobiotics. Cytochrome P450 enzymes, a large group of oxidizing enzymes, are involved in the corresponding metabolic transformations. On the other hand, reductions are of crucial importance for the organism too. In these reaction steps, reactive aldehydes or ketones are transformed into alcohols, which subsequently are more easily conjugated and eliminated (Sect. 8.1). Transition metals, which can adopt a variety of oxidation states, are predestined to serve as electron donors and acceptors in redox reactions. In biological systems, one transition metal, iron, is often used for this task. Once incorporated in a protoporphyrin ring scaffold, it exists in penta- or hexavalent coordination state and can take on oxidation states between +2 and +4. Moreover, it participates in complexes with sulfur. There it forms interesting multinuclear structures: the so-called iron–sulfur cluster. In addition to iron, copper also plays a role as a mediator of biochemical redox processes.