May be a redox sensor protein. Has much higher affinity for NAD(P) than for NAD(P)H. Has similar affinity for NAD and NADP. Negative transcriptional regulator involved in the post-transcriptional modulation of the GATA-type transcription factor areA, forming part of a system controlling nitrogen metabolite repression (By similarity). Interferes with the interaction between areA and target DNA. Overexpression leads to areA inhibition. Monomer. Interacts with areA. Up-regulated in nitrogen-sufficient conditions and down-regulated in nitrogen-limiting conditions. Displays partial derepression of activities subject to nitrogen metabolic repression. Belongs to the NmrA-type oxidoreductase family. Lacks the conserved Tyr residue in position 127 in the active site triad of Ser-Tyr-Lys that is necessary for dehydrogenase activity, suggesting that it has no oxidoreductase activity.