A LYSINE DEHYDROGENASE-BASED ELECTRODE FOR BIOSENSING OF L-LYSINE

An amperometric biosensor for L-lysine based on the recently isolated enzyme lysine dehydrogenase is described. Immobilization of the enzyme onto a platinum electrode is achieved via entrapment within a gelatin support on a cellulose membrane. Anodic detection (at 0.4 V vs. Ag/AgCl) is facilitated by the presence of a redox-mediating ferricyanide ion. The effect of experimental variables such as pH, enzyme loading, applied potential, cofactor and mediator concentrations were evaluated in order to optimize the analytical performance. A detection limit of 7 X 10(-8) M, and linearity up to 7 X 10(-4) M are reported. The fast response permits adaptation for flow injection operation with good precision (RSD = 1.9%) and high sample throughput (40 samples per hour). The high specificity offered by this new enzyme is indicated by the lack of interference by other L-amino acids, alcohols or carbohydrates.