(A) Parkinson's # MPTP induces parkinsonism in humans and animal models, whereas the b-carbolines were postulated as possible toxins involved in neurodegeneration.> A so-called 'activation' to toxic pyridinium or b-carbolineum species is required for toxicity, whereas an 'inactivation' may influence the fate of these protoxins in the body potential involvement of peroxidases in neurodegeneration and Parkinson's disease has been already suggested.> Myeloperoxidase occurs at sites of degenerative diseases and neuroinflammation and increases in Alzheimer's disease, and its ablation mitigated PD produced by MPTP neurotoxin in animals.