Monoubiquitination of the residues near the active site of UCHL1 can restrict its enzymatic activity by inhibiting the binding of Ub to UCHL1 (Table 3), promoting the progression of neurodegenerative diseases, including Alzheimer’s and Parkinson’s disease (Das et al., 2006; Meray and Lansbury, 2007; Liu et al., 2009). The gene discussed is UCHL1; the disease is Parkinson disease.