UCHL1(Ubiquitin carboxyl-terminal hydrolase isozyme L1) is a member of a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to generate the ubiquitin monomer. Expression of UCHL1 is highly specific to neurons and to cells of the diffuse neuroendocrine system and their tumors. It is present in all neurons. This protein is present in brain at concentrations at least 50 times greater than in other organs and is a major protein component of neuronal cytoplasm . And UCHL1 is a Parkinson's disease susceptibility gene .