PRKN and Parkinson disease: In addition, gene encoding ubiquitin carboxyl-terminal hydroxylase (UCH-L1), and genes on chromosomes X, 1, 2, and 4, also have influential roles in the etiology of PD in some families [16].(i)Parkin. Parkin is an important protein associated with protein clearance pathways, such as ubiquitin-proteasome system, which can help degrade misfolded proteins in the cell (Table 1).