This family contains only archaeal MPN (also known as Mov34, PAD-1, JAMM, JAB, MPN+)-like domains. These domains contain the signature JAB1/MPN/Mov34 metalloenzyme (JAMM) motif, EXnHS/THX7SXXD, which is involved in zinc ion coordination and provides the active site for isopeptidase activity for the release of ubiquitin from ubiquitinated proteins (thus having deubiquitinating (DUB) activity) that are tagged for degradation. The JAMM proteins likely hydrolyze ubiquitin conjugates in a manner similar to thermolysin, in which the zinc-polarized aqua ligand serves as the nucleophile, compared with the classical DUBs that do so with a cysteine residue in the active site.
Jiyao W et al.(2023). "The conserved domain database in 2023.",