Patent ID: 7169273

Claim:
An enzyme electrode comprising: (a) an electrode system comprising an insulating substrate having formed thereon a working electrode, a counter electrode and optionally a reference electrode; and (b) a reaction layer formed on said electrode system, wherein said reaction layer comprises diaphorase (DI), 12α-hydroxysteroid dehydrogenase (12α-HSD) and nicotinamide adenine dinucleotide synthetase (NADS), at least a portion of said reaction layer being superposed on said working electrode, wherein the DI, 12α-HSD and NADS contained in said portion of the reaction layer are immobilized on the surface of said working electrode, so that a compound generated in said reaction layer can reach the surface of said working electrode, and wherein, with respect to said portion of the reaction layer which is superposed on said working electrode; the total amount of proteins is 2.5 mg or less per cm 2 of said portion of said reaction layer; the amount of DI in terms of the activity thereof is 0.25 U or more per cm 2 of said portion of said reaction layer; the amount of 12α-HSD in terms of the activity thereof is 0.63 U or more per cm 2 of said portion of said reaction layer; and the amount of NADS in terms of the activity thereof is 0.063 U or more per cm 2 of said portion of said reaction layer.