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-met hyl-guanine and guanine respectively (Nm(7)GD(+) and NGD(+)) were exam ined electrochemically, enzymatically and by UV and fluorescence spect roscopy. The enzymatic activity of Nm(7)GD(+) and NGD(+) with yeast al cohol 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 solution s was examined polarographically and by macroscale electrolysis. The m echanism of the reduction process was formulated. The surface activiti es of Nm(7)GD(+) and NGD(+) were confirmed by ac polarography. Intramo lecular interactions of Nm(7)GD(+) at pH 5.0 and 8.93 were studied by fluorescence measurements, and the thermodynamic parameters for this p rocess were determined.