Human DUBs consist of two classes of enzymes: cysteine proteases and metalloproteases. Cysteine proteases are further subdivided into five families, including ubiquitin-specific proteases (USPs), ubiquitin carboxyl-terminal hydrolases (UCHs), ovarian tumor proteases (OTUs), Machado-Joseph (Josephin) domain containing (MJD) proteases, and MINDY (motif interacting with Ub-containing novel DUB family). The JAB1/MPN/MOV34 domain containing proteases (JAMMs) family is the only representative of the metalloproteases class of DUBs. Adapted from (2).