Diaphorase (DI) works as an effective catalyst for the electrochemical oxidation and reduction of NAD with the aid of several quinones or flavins as electron transfer mediators. The redox kinetics between DI and mediators have been expressed by a Butler-Volmer-type equation. NAD-dependent L-lactate dehydrogenase (LDH) catalyzing the redox reaction between L-lactate and pyruvate was coupled to the DI-catalyzed NAD redox system to achieve better understanding of mediated two-enzyme-linked bioelectrocatalysis with reversible characteristics. Under the conditions where the concentration polarization of NAD due to the DI-catalyzed electrochemical reaction is suppressed by the LDH reaction, the NAD concentration dependence of the catalytic current was expressed by an approximate equation involving the enzyme kinetics between DI and NAD. The suppression of the NAD concentration polarization is also useful to observe steady-state catalytic waves of an uphill reaction between DI and the mediator. The oxidation reaction involving the uphill electron transfer from L-lactate to NAD(+) is susceptible to a inhibition from pyruvate due to the reversible characteristics of LDH. The present knowledge has led to the strategy to realize a two-way bioelectrocatalysis for the reduction of pyruvate and the oxidation of L-lactate. New potentiometry for the detection of the solution potential governed by the electrochemically inactive pyruvate/L-lactate redox couple has also been demonstrated based on the reversible characteristics of the DI-DLH-linked bioelectrocatalytic system.