... Under these conditions, 1 unit of the enzymewas defined as the amount of enzyme catalyzing the produc-tion of 1 lmol of NADH per min. An extinction coefficient of 6.22 per mm for NADH was utilized ... [4,5,31–33]. In the structure of humanm-NAD-ME, besides the active site, there are tworegulatory sites (Fig. 1A). One of them, located at thetetramer interface and called the exo site, is occupiedby ... K0.5,Malatevalues of E59D were 2-fold and4.4-fold higher, respectively, than that of the wild-type.Furthermore, the kcatvalue of E59 mutant enzymeswas only one-third to one-quarter of that of thewild-type,...