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:15703176, PubMed:16835243, PubMed:17337452, PubMed:17217311, PubMed:23614568, PubMed:28691797, PubMed:29787766, PubMed:31990367, PubMed:22329685). Hydrolyzes adenosine 5'monophosphomorpholidate (AMP-morpholidate) and guanosine 5'monophosphomorpholidate (GMP-morpholidate) (PubMed:15703176, PubMed:16835243). Hydrolyzes lysyl-AMP (AMP-N-epsilon-(N-alpha-acetyl lysine methyl ester)) generated by lysine tRNA ligase, as well as Met-AMP, His-AMP and Asp-AMP, lysyl-GMP (GMP-N-epsilon-(N-alpha-acetyl lysine methyl ester)) and AMP-N-alanine methyl ester (PubMed:15703176, PubMed:22329685, PubMed:17337452). Hydrolyzes 3-indolepropionic acyl-adenylate, tryptamine adenosine phosphoramidate monoester and other fluorogenic purine nucleoside tryptamine phosphoramidates in vitro (PubMed:17337452, PubMed:23614568, PubMed:29787766, PubMed:17217311, PubMed:28691797, PubMed:31990367). Can also convert adenosine 5'-O-phosphorothioate and guanosine 5'-O-phosphorothioate to the corresponding nucleoside 5'-O-phosphates with concomitant release of hydrogen sulfide (PubMed:30772266). In addition, functions as scaffolding protein that modulates transcriptional activation by the LEF1/TCF1-CTNNB1 complex and by the complex formed with MITF and CTNNB1 (PubMed:16014379, PubMed:22647378). Modulates p53/TP53 levels and p53/TP53-mediated apoptosis (PubMed:16835243). Modulates proteasomal degradation of target proteins by the SCF (SKP2-CUL1-F-box protein) E3 ubiquitin-protein ligase complex (PubMed:19112177). Also exhibits SUMO-specific isopeptidase activity, deconjugating SUMO1 from RGS17 (PubMed:31088288). Deconjugates SUMO1 from RANGAP1 (By similarity). adenosine 5'-phosphoramidate + H2O = AMP + NH4(+) Homodimer. Interacts with CDK7. Interacts with RUVBL1 and RUVBL2 and is associated with the LEF1/TCF1-CTNNB1 complex and with a KAT5 histone acetyltransferase complex. Identified in a complex with MITF and CTNNB1. Interacts with CDC34 and RBX1, and is part of a SCF (SKP2-CUL1-F-box protein) E3 ubiquitin-protein ligase complex (PubMed:19112177). Interacts with SUMO1, SUMO2 and RGS17 (By similarity). Interacts with the Ten-1 ICD form of TENM1 (By similarity). Interacts with CALM1; interaction increases in the presence of calcium ions (By similarity). Interaction with CDK7 leads to a more nuclear localization. Widely expressed. The disease is caused by variants affecting the gene represented in this entry. Belongs to the HINT family. Was originally thought to be a protein kinase C inhibitor and to bind zinc in solution. Both seem to be incorrect.