Determination of enzyme activity in biological fluids by means of electrochemical oxidation of NADH at a modified glassy carbon electrode.

This amperometric technique for the determination of enzyme activity is based on detecting a decrease in the concentration of the NADH co-factor of the enzyme reaction. A glassy carbon electrode, modified by adsorption of Mg2+ and NADH, is used to measure the anodic peak current that corresponds to the oxidation of NADH. We found no significant difference between the enzyme activity of lactate dehydrogenase (E.C.1.1.1.27) preparations as measured by the above amperometric technique and by a spectrophotometric method.