In enzymology, a nicotinamide-nucleotide amidase (EC 3.5.1.42) is an enzyme that catalyzes the chemical reaction

beta-nicotinamide D-ribonucleotide + H₂O beta-nicotinate D-ribonucleotide + NH₃

Thus, the two substrates of this enzyme are beta-nicotinamide D-ribonucleotide and H₂O, whereas its two products are beta-nicotinate D-ribonucleotide and NH₃.

This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in linear amides. The systematic name of this enzyme class is nicotinamide-D-ribonucleotide amidohydrolase. Other names in common use include NMN deamidase, nicotinamide mononucleotide deamidase, and nicotinamide mononucleotide amidohydrolase. This enzyme participates in nicotinate and nicotinamide metabolism.

• Imai T (January 1973). "Purification and properties of nicotinamide mononucleotide amidohydrolase from Azotobacter vinelandii". Journal of Biochemistry. 73 (1): 139–53. PMID 4144084.