ASSAY OF DEHYDROGENASES WITH AN O-2-CONSUMING BIOSENSOR

Coimmobilization of L-lactate oxidase (LOD) and L-lactate dehydrogenas e (LDH) on a film bound to an oxygen electrode makes it possible, by r ecycling L-lactate and pyruvate, to lower their detection limit to 10 nM. With LOD immobilized alone and LDH in solution easy LDH measuremen ts were performed. The detection limit was 1 IU l(-1). Similarly, this mixed biosensor, using an LDH sensitive to mercurials, was used for p -chloromercuribenzoate (PCMB) detection. Coimmobilization of LOD + LDH with an NAD(+)-dependent dehydrogenase allows the measurements of all dehydrogenases. NAD(+) is recycled. The detection limit was 50 nM. Ap plications can be found in medicine, the food industry, and the enviro nment.