Exhibits adenosine 5'-monophosphoramidase activity, hydrolyzing purine nucleotide phosphoramidates with a single phosphate group such as adenosine 5'monophosphoramidate (AMP-NH2) to yield AMP and NH2 (By similarity). Hydrolyzes lysyl-AMP (AMP-N-epsilon-(N-alpha-acetyl lysine methyl ester)) generated by lysine tRNA ligase (By similarity). adenosine 5'-phosphoramidate + H2O = AMP + NH4(+) Forms dimers to octamers and even larger oligomer. Belongs to the HINT family.