Ubiquitin C-terminal hydrolases are a family of cysteine hydrolases that catalyze the hydrolysis of amides, esters and thioesters from the C-terminus of ubiquitin. UCH-L1 is a member of the low molecular weight UCHs that processes ubiquitin precursors and ubiquitinated proteins to generate monomeric ubiquitin. The expression of UCH-L1 is highly specific to cells of the neuroendocrine system and their tumors. UCH-L1 variants (Ile⁹³Met) have been linked to Parkinson disease and may participate in processes critical for neuronal health.