ELECTROCHEMICAL AND SPECTROSCOPIC STUDY OF REDOX TRANSFORMATION OF THE 7-METHYLGUANINE ANALOG OF COENZYME NAD(+)

Two NAD(+) analogs in which the adenine moiety is substituted by 7-methyl-guanine and guanine respectively (Nm(7)GD(+) and NGD(+)) were examined electrochemically, enzymatically and by UV and fluorescence spectroscopy. The enzymatic activity of Nm(7)GD(+) and NGD(+) with yeast alcohol dehydrogenase was studied. The kinetic parameters K-m and V-max for the enzymatic reduction of the two compounds were determined. The electrochemical reduction of Nm(7)GD(+) and NGD(+) in aqueous solutions was examined polarographically and by macroscale electrolysis. The mechanism of the reduction process was formulated. The surface activities of Nm(7)GD(+) and NGD(+) were confirmed by ac polarography. Intramolecular interactions of Nm(7)GD(+) at pH 5.0 and 8.93 were studied by fluorescence measurements, and the thermodynamic parameters for this process were determined.