Hydrolyzes adenosine 5'-monophosphoramidate substrates such as AMP-morpholidate, AMP-N-alanine methyl ester, AMP-alpha-acetyl lysine methyl ester and AMP-NH2. adenosine 5'-phosphoramidate + H2O = AMP + NH4(+) Homodimer. Belongs to the HINT family.