Monoamine oxidase-B (MAO-B) is a FAD-dependent mitochondrial enzyme, which, together with its isoenzyme MAO-A, catalyzes the oxidative deamination of structurally diverse amines Kalgutkar et al. (2001). MAO-B is involved in the metabolism of biogenic amines as well as amine xenobiotics Cesura and Pletscher (1992). Substrates preferential for MAO-B include 2-phenylethylamine and benzylamine. Other substrates, e.g., dopamine and tyramine, show similar Km values for MAO-B and MAO-A Tipton et al. (1987), Waldmeier (1987). Among the xenobiotic amines metabolized by MAO-B, the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) has received particular attention due to its properties to induce a syndrome closely resembling Parkinson's disease. In fact, MAO-B plays a major role in the transformation of MPTP into 1-methyl-4-phenylpyridinium (MPP+), the species responsible for the neurotoxic effects Langston et al. (1983), Markey et al. (1984).
The MAO-B inhibitor L-deprenyl is in clinical use for the treatment of Parkinson's disease and, currently, several MAO-B inhibitors are under clinical investigation in Parkinson's and Alzheimer's disease.
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