Zinc metalloprotease that specifically cleaves 'Lys-63'-linked polyubiquitin chains. Does not cleave 'Lys-48'-linked polyubiquitin chains. Plays a role in signal transduction for cell growth and MYC induction mediated by IL-2 and GM-CSF. Potentiates BMP (bone morphogenetic protein) signaling by antagonizing the inhibitory action of SMAD6 and SMAD7. Has a key role in regulation of cell surface receptor-mediated endocytosis and ubiquitin-dependent sorting of receptors to lysosomes. Endosomal localization of STAMBP is required for efficient EGFR degradation but not for its internalization. Involved in the negative regulation of PI3K-AKT-mTOR and RAS-MAP signaling pathways. Binds 2 Zn(2+) ions per subunit. Inhibited by N-ethylmaleimide. Interacts with STAM. Interacts with SMAD6 and SMAD7. Interacts with CHMP3; the interaction appears to relieve the autoinhibition of CHMP3. Interacts with SMURF2 and RNF11; this interaction promotes ubiquitination. The JAMM motif is essential for the protease activity. Phosphorylated after BMP type I receptor activation. Ubiquitinated by SMURF2 in the presence of RNF11. Belongs to the peptidase M67C family.