Amperometric enzyme electrode for the determination of aspartate aminotransferase and alanine aminotransferase in serum

Glutamate oxidase (E.C. 1.4.3.7) was immobilized at a platinized activated carbon electrode and the enzyme electrodes were used for the amperometric determination of L-glutamate in a stirred aqueous solution by the electrochemical detection of enzymically produced hydrogen peroxide at + 320 mV vs. Ag/AgCl. A linear calibration graph was obtained between 2 μM and 2 mM with a steady-state response time of 1 min. The glutamate oxidase electrode was subsequently applied to the measurement of aspartate aminotransferase (AST) (E.C. 2.6.1.1) and alanine aminotransferase (ALT) (E.C. 2.6.1.2) in serum. The performance of the electrode was compared with that of techniques used in the hospital diagnostic laboratory. The responses of the enzyme electrode to AST and ALT activities were linear over the clinically relevant range (5-500 U l ^?1), and correlated well (r=0.99) with the methods used for routine clinical analysis.