Figure 1.

Inhibitory effects of NADH on the αγ, αβ and α₂βγ enzymes of human NAD-IDH. The enzymatic activities of the αγ and α₂βγ enzymes in the presence of NADH were measured at the standard conditions with varied concentrations of NADH as described in “Methods”. The activity of the αβ enzyme was determined at the same conditions except for a higher concentration of MnCl₂ (50 mM). The inhibitory effect of NADH on the activity of the enzyme is presented as percent of inhibition (I) as a function of NADH concentration. I = (V₀−V)/V₀ * 100, where V₀ and V are the initial velocities in the absence and presence of NADH, respectively.