Zinc metalloprotease that specifically cleaves 'Lys-63'- linked polyubiquitin chains (PubMed:15314065, PubMed:23542699, PubMed:34425109). Does not cleave 'Lys-48'-linked polyubiquitin chains (PubMed:15314065). Plays a role in signal transduction for cell growth and MYC induction mediated by IL-2 and GM-CSF (PubMed:10383417). Potentiates BMP (bone morphogenetic protein) signaling by antagonizing the inhibitory action of SMAD6 and SMAD7 (PubMed:11483516). Has a key role in regulation of cell surface receptor-mediated endocytosis and ubiquitin-dependent sorting of receptors to lysosomes (PubMed:15314065, PubMed:17261583). Endosomal localization of STAMBP is required for efficient EGFR degradation but not for its internalization (PubMed:15314065, PubMed:17261583). Involved in the negative regulation of PI3K-AKT-mTOR and RAS-MAP signaling pathways (PubMed:23542699). {ECO:0000269|PubMed:10383417, ECO:0000269|PubMed:11483516, ECO:0000269|PubMed:15314065, ECO:0000269|PubMed:17261583, ECO:0000269|PubMed:23542699, ECO:0000269|PubMed:34425109}. This is the function of Ensembl gene identifier ENSG00000124356 (STAMBP, STAM binding protein).