Deubiquitinating enzymes (DUBs) can be classified based on their active site homology into two main classes: cysteine proteases and zinc metalloproteases. Of these two classes, there are five families of cysteine protease DUBs and one family of zinc metalloprotease DUBs. The five families of cysteine protease DUBs consist of motif interacting with Ub-containing novel DUB family (MINDY), ubiquitin-specific protease (USP/UBP), ubiquitin carboxyl-terminal hydrolase (UCH), zinc finger with UFM1-specific peptidase domain protein (ZUFSP), ovarian tumor (OTU), and Machado-Josephin domain (MJD). The one family of zinc metalloprotease DUBs consist of Jab1/Mov34/Mpr1 Pad1 N-terminal+ (MPN+) (JAMM).