UCH-L3 (Ubiquitin carboxyterminal hydrolase isozyme 3) is a 26-28kD member of the peptidase C12 family of enzymes. It shows wide expression, being noted in adipocytes, renal duct epithelium, neurons, and striated muscle. UCH-L3 cleaves both monomeric ubiquitin (Ub) from Ub-protein conjugates, and a GGLRQ peptide from the C-terminus of the Ub-like protein NEDD-8. Notably, UCH-L3 activity is muted in the presence of Ub interacting dimers. Human UCH-L3 is 230aa in length. It is phosphorylated on Ser75 and Ser130, and contains two ubiquitin-binding sequences between aa40-57 and 178-186. Four potential splice forms have been reported. Two show a four aa deletion between aa15-18, with one also containing a 14aa substitution for aa179-230. Two others contain an alternative start site at Met37, one of which is also accompanied by a seven aa substitution for aa143-230. Full-length human UCH-L3 shares 98% aa identity with mouse and rat UCH-L3.