The nigrostriatal toxin l-methyl-l-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) is an excellent substrate and a weak inactivator of the flavoenzyme monoamine oxidase B (MAO-B). In an attempt to develop novel mechanism-based inactivators of MAO-B, we have synthesized analogs of MPTP bearing a variety of functional groups at either the N or the C (4) position and have examined their interactions with a purified MAO-B preparation isolated from beef ...