Human Cytochrome P450 2C9 and its Polymorphic Modifications: Electroanalysis, Catalytic Properties and Approaches to the Regulation of Enzymatic Activity

The electrochemical properties of cytochrome P450 2C9 (CYP2C9) and polymorphic modifications P450 2C9*2 (CYP2C9*2) and P450 2C9*3 (CYP2C9*3) were studied. To analyze the comparative catalytic activity, the enzymes were immobilized on electrodes modified with a membrane-like synthetic surfactant (didodecyldimethylammonium bromide (SPE/DDAB). Peaks of reduction and oxidation of the heme iron, which confirms the adequate choice of the type of modified electrode, characterize cyclic voltammograms of cytochromes P450 under anaerobic conditions. The midpoint potential, Emid, of cytochrome P450 2C9 was -0.318 ± 0.01 V, and Emid =-0.324 ± 0.01 V, and Emid = -0.318 ± 0.03 V for allelic variant 2C9*2 and allelic variant 2C9*3, respectively. In the presence of substrate diclofenac under aerobic conditions, cytochrome P450 2C9 and its polymorphic modifications P450 2C9*2 and P450 2C9*3 exhibit catalytic properties registered by increasing the catalytic current. The amplitude ratio of diclofenac/oxygen currents ((IDF/IO2, catalytic index) is 1.80 for cytochrome P450 2C9, 1.33 and 2.18 for isoforms 2C9 *2 and 2C9*3, respectively. Antioxidant medications mexidol and taurine (at a concentration of 98 μM and 100 μM, respectively) stimulated aerobic reduction of cytochromes P450 heme iron. In the presence of mexidol, an increase in the catalytic activity of cytochrome P450 2C9 in relation to diclofenac by 1.7 times is registered. Taurine, vitamin-like compound with antioxidant properties also stimulates the metabolism of diclofenac by 1.5 times.