Parkin (Parkinson juvenile disease protein 2) is a ~52 kDa E3 Ligase enzyme protein, encoded by PARK2 gene. It plays an important role in the ubiquitin-proteasome system and acts as a regulator of protein breakdown. Parkin is located in the cytoplasma until a sustained depolarization occurs after which it is translocated to the mitochondrial membrane and induces the degradation of various membrane proteins. Parkin mutation leads to the accumulation of missfolded, aggregated proteins and degenerated mitochondria. The role of these changes in the pathomechanism of neurodegenerative diseases is well-known. Present views are that the improper regulation of protein aggregation and a dysfunction of the ubiquitin-proteasome system may be the common pathway of sporadic and hereditary Parkinson’s disease.