Being a protoxin, MPTP undergoes bioactivation by monoamine oxidase B (MAO B), the enzyme of the outer mitochondrial membrane; the resultant neurotoxin MPP+ (1-methyl-4-phenylpyridinium) inhibits complex I of the mitochondrial respiratory chain, thus promoting the development of mitochondrial dysfunction and movement disorders typical of Parkinson’s disease [3,4,5]. The gene discussed is MAOB; the disease is movement disorder.