UCHL1 and Parkinson disease: Its role in the development of PD is determined by several major issues: (a) UCHL1 is a unique enzyme responsible for ubiquitin precursor processing; (b) UCHL1 interacts with many important intracellular targets, including PD-related proteins; (c) mutations, posttranslational modifications of UCHL1, and interactions with PD-related proteins have a profound effect on cell functioning.