Park7 (DJ-1) is a small protein of 189 amino acids that is ubiquitously expressed in almost all cells and tissues, including the brain. It exists as a homodimer and is localized to the cytoplasm, mitochondria, and nucleus. DJ-1 belongs to the ThiJ/PfpI protein superfamily and is highly conserved across all biological kingdoms. Mutations in the Park7 gene, including L166P or deletions, are associated with an early-onset form of familial Parkinson's disease (PD). DJ-1 plays remarkable roles in mitochondrial function and antioxidant effects, and its overexpression can protect cells against dopamine- or MPTP-induced neurotoxicity and oxidative stress. DJ-1 is thought to act as a sensor of cellular redox homeostasis and participate in cytoprotective signaling pathways within the cell. Under oxidative stress, a conserved cysteine residue in DJ-1 (Cys106) is oxidized, which is believed to enable the neuroprotective activity of DJ-1. DJ-1 interacts with various proteins, including RACK1 and MAO-B, to regulate cellular signaling and protect against neurotoxicity. The loss of DJ-1 function can lead to the upregulation of MAO-B, contributing to dopamine metabolic dysfunction and neurodegeneration.