This is particularly true of neurodegenerative disorders; the current symptomatic treatment of both Parkinson’s (PD) and Alzheimer’s (AD) diseases owes everything to the findings of brain neurotransmitter deficits—dopamine in PD, leading directly to replacement therapy with levodopa, and acetylcholine in AD, indicating the potential for cholinesterase inhibition. Here, BCHE is linked to Parkinson disease.