Phosphatase which catalyzes the conversion of NADP(+) to NAD(+) and of NADPH to NADH (By similarity). Shows a small preference for NADPH over NADP(+) (By similarity). Component of the circadian clock or downstream effector of clock function (PubMed:12573214). Exhibits a high amplitude circadian rhythm with maximal levels in early evening (PubMed:12573214). In constant darkness or constant light, the amplitude of the rhythm decreases (PubMed:12573214). H2O + NADP(+) = NAD(+) + phosphate H2O + NADPH = NADH + phosphate Binds 2 magnesium ions, but the ions are only loosely bound to the protein. Expressed only in the photoreceptors of the retina. Expression is controlled by the retinal circadian clock. Belongs to the CCR4/nocturin family. Was initially shown to have low deadenylase activity that was lost when the metal-binding Glu was mutated (PubMed:12573214). Later studies showed that the purified protein lacked deadenylase activity (By similarity). Was subsequently shown to act as a phosphatase (By similarity).