A GAC to TAC change resulting in an aspartate to tyrosine substitution at amino acid 331 (D331Y) was generated in exon 7. A loxP-flanked neomycin selection cassette was inserted 401 nucleotides downstream of the start of exon 7. The neomycin selection cassette was removed via cre-mediated recombination. The p.Asp331Tyr is thought to be the causative mutation of Parkinson's disease 14 in patients. Western blot analysis confirmed similar cytosolic or mitochondrial protein expression as in wild-type mice, however enzyme activity is significantly decreased in the substantia nigra indicting loss of function.