Zinc metalloprotease that specifically cleaves 'Lys-63'-linked polyubiquitin chains. 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. Does not cleave 'Lys-48'-linked polyubiquitin chains. Binds 2 Zn(2+) ions per subunit. Ubiquitously expressed. Isoform 1 is widely expressed while isoform 2 is testis-specific. The JAMM motif is essential for the protease activity. Belongs to the peptidase M67C family.