Parkin is thought to play a role in the ubiquitin/proteasome pathway for protein degradation. The amino terminus bears sequence homology to ubiquitin while functionally it acts as a RING-type ubiquitin protein ligase (E3) that coordinates the transfer of ubiquitin to substrate proteins, thus targeting them for degradation by the proteasome. Mutations in the human version of the protein are known to cause autosomal recessive juvenile parkinsonism.