Deubiquitinating enzymes (DUBs) are proteases that posses the ability to cleave ubiquitin chains or the isopeptide bond that conjugates ubiquitin with a substrate. Human cells have approximately 100 DUBs that play important roles in regulating various cellular events. UCHL1 is one of the four members of the ubiquitin C-terminal hydrolase (UCH) family. It is thought to be mainly involved in cleaving proubiquitin proteins into monomeric ubiquitin.