Ubiquitin carboxyl-terminal hydrolase isozyme L3, also known as UCH-L3, Ubiquitin thioesterase L3 and UCHL3, is a ubiquitin-protein hydrolase that belongs to the peptidase C12 family. It is involved both in the processing of ubiquitin precursors and of ubiquitinated proteins. This enzyme is a thiol protease that recognizes and hydrolyzes a peptide bond at the C-terminal glycine of either ubiquitin or NEDD8. UCHL3 is highly expressed in heart, skeletal muscle, and testis. UCHL1 and UCHL3 are two of the deubiquitinating enzymes expressed in the brain. These phenotypes indicate the importance of UCHL1 and UCHL3 in the regulation of the central nervous system. UCHL3 functions as a de-ubiquitinating enzyme where lack of its hydrolase activity may result in the prominent accumulation of ubiquitinated proteins and subsequent induction of stress responses in skeletal muscle. UCHL3 has also been identified as a tumor-specific antigen in colon cancer.