Studies have shown that mutations in the PreP (Pre-sequence Protease) and DJ-1/PARK (Parkinson-associated gene DJ-1) genes, as well as mitochondrial stress associated with inhibition of the PDI (protein disulfide isomerase) enzyme, which promotes NO accumulation via the Glutamate receptor (NMDAR) in the brain cell membrane, cause Alzheimer's and Parkinson's in humans (Uehara et al. 2006). The gene discussed is P4HB; the disease is Parkinsonism.