Ubiquitin Carboxyl-terminal Esterase L3 (UCH-L3) is a member of the peptidase C12 family of deubiquitinating enzymes. It is widely expressed with the highest levels being observed in heart, testis, thymus and striated muscle. UCH-L3 is 230 amino acids (aa) in length with a predicted molecular weight of 26.1 kDa. It is composed of a single N-terminal UCH domain with a short active-site crossover loop allowing UCH-L3 to process small Ubiquitin derivatives. Human UCH-L3 shares 98% aa sequence identity with the mouse and rat orthologs. UCH-L3 releases monomeric Ubiquitin from Ubiquitin-protein conjugates. Additionally, it cleaves a GGLRQ peptide from the C-terminus of the Ubiquitin-like protein NEDD-8, allowing NEDD8 to be conjugated to target proteins. UCH-L3 activity is muted in the presence of Ubiquitin dimers. UCH-L3 is suggested to function in the central nervous system. In particular, it is involved in the maintenance of neurons of the gracile tract, nucleus tractus solitaris, and area postrema, and in working memory. UCH-L3 has also been shown to modulate germ cell apoptosis and promote insulin signaling and adipogenesis. Additionally, UCH-L3 expression has been shown to be correlated with cancer.