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 (PubMed:17870088). Hydrolyzes lysyl-AMP (AMP-N-epsilon-(N-alpha-acetyl lysine methyl ester)) generated by lysine tRNA ligase (PubMed:17870088). Hydrolyzes 3-indolepropionic acyl-adenylate and fluorogenic purine nucleoside tryptamine phosphoramidates in vitro (PubMed:17870088). adenosine 5'-phosphoramidate + H2O = AMP + NH4(+) HINT3 prefers purine over pyrimidine-based substrates. Forms dimers to octamers and even larger oligomer (PubMed:17870088). Interacts with CALM1 (By similarity). Localized as aggregates in the cytoplasm and the nucleus. Belongs to the HINT family.