From Proteopediaproteopedia link
Solution structure of UCHL1 S18Y variant
[UCHL1_HUMAN] Defects in UCHL1 are the cause of Parkinson disease type 5 (PARK5) [MIM:613643]; also known as Parkinson disease autosomal dominant 5. PARK5 is a complex neurodegenerative disorder with manifestations ranging from typical Parkinson disease to dementia with Lewy bodies. Clinical features include parkinsonian symptoms (resting tremor, rigidity, postural instability and bradykinesia), dementia, diffuse Lewy body pathology, autonomic dysfunction, hallucinations and paranoia.   
[UCHL1_HUMAN] 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.