Zinc metalloprotease that specifically cleaves 'Lys-63'-linked polyubiquitin chains (PubMed:18758443, PubMed:35114100). Acts as a positive regulator of the TORC1 signaling pathway by mediating 'Lys-63'-linked deubiquitination of SESN2, thereby inhibiting SESN2-interaction with the GATOR2 complex (PubMed:35114100). Does not cleave 'Lys-48'-linked polyubiquitin chains (PubMed:18758443). Binds 2 Zn(2+) ions per subunit. Inhibited by UbV(SP.1), an ubiquitin variant that also inhibits STAMBP. Ubiquitously expressed. The JAMM motif is essential for the protease activity. Belongs to the peptidase M67C family.