Acts equally well on hydrated NADH and hydrated NADPH. NAD(P)H spontaneously hydrates to both the (6S)- and (6R)- isomers, and these are interconverted by EC?5.1.99.6, NAD(P)H-hydrate epimerase, to a 60:40 ratio [4]. Hence EC?4.2.1.93?together with EC?5.1.99.6?can restore the mixture of hydrates into NAD(P)H [3,4]. The enzyme from eukaryotes has no activity with ADP, contrary to the enzyme from bacteria (cf. EC?4.2.1.136, ADP-dependent NAD(P)H-hydrate dehydratase) [4].