HINT3 (histidine triad nucleotide binding protein 3) is a member of the HIT superfamily that functions as an adenosine 5'-monophosphoramidase, hydrolyzing purine nucleotide phosphoramidates such as adenosine 5'-monophosphoramidate to yield AMP and NH2 1. The enzyme also hydrolyzes lysyl-AMP generated by lysyl-tRNA synthetase and exhibits activity toward synthetic substrates like indolepropionic acyl-adenylate and fluorogenic purine nucleoside phosphoramidates 1. HINT3 demonstrates unique structural characteristics within the HIT family, existing in variable oligomeric states from dimers to octamers, unlike other HIT proteins that form exclusively homodimers, and localizes to both cytoplasm and nucleus 1. Recent structural modeling suggests HINT3 is more similar to Aprataxin than to HINT1/HINT2, containing a distinctive α3 helix and potential disulfide bond sites 2. In cancer biology, HINT3 functions as a tumor suppressor in breast cancer by transcriptionally activating PTEN, leading to suppression of AKT/mTOR signaling and inhibition of cell proliferation, migration, and tumorigenesis 3. HINT3 expression is downregulated in various cancers including breast cancer and endometriosis, suggesting its loss contributes to disease pathogenesis 34.