Effect of L-aspartate concentration on the response of the amperometric L-glutamate sensor for the measurement of L-glutamate and aspartate aminotransferase activity in serum

L-glutamate oxidase was immobilized in a photo-cross-linkable polymer membrane on a palladium strip electrode for the amperometric measurement of aspartate aminotransferas eactivity. The sample, serum for example, was injected into a buffered L-aspartate and alpha-ketoglutarate solution. L-aspartate is the essential substrate and can transfer to L-glutamate via the aspartate aminotransferase catalyzing reaction. Aspartate aminotransferase activity can be measured by determining the increasing rate of L-glutamate. Under the optimal condition, the current increasing rate was proportional to the aspartate aminotransferase activity of the sample in the range of 8-200 U/L. The data are in good correlation (R-2 = 0.998) with data from a commercial aspartate aminotransferase assay kit. Good reproducibility (relative standard deviation = 3.03%, n = 8) was obtained from a sample with 50 U/L aspartate aminotransferase activity. The sensor is expectable to be applied in a clinical point-of-care diagnosis.