Synonyms:Neuron cytoplasmic protein 9.5, PARK5, PGP 9.5, PGP9.5, Ubiquitin thioesterase L1, Uch L1, UCHL1 Background:Ubiquitin-protein hydrolase 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 ubiquitin. Also binds to free monoubiquitin and may prevent its degradation in lysosomes. The homodimer may have ATP-independent ubiquitin ligase activity.