Oxidation of the neurotoxic amine 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidases A and B and suicide inactivation of the enzymes by MPTP

Biochem Biophys Res Commun. 1984 Dec 14;125(2):831-5. doi: 10.1016/0006-291x(84)90614-4.


1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a thermal breakdown product of a meperidine-like narcotic analgetic used by drug abusers as a synthetic heroin, causes Parkinsonian symptoms in humans and degeneration of the substantia nigra in monkeys. MPTP is oxidized by brain mitochondrial preparations in a process which is blocked by deprenyl and pargyline, implying catalysis by monoamine oxidase B. The present paper demonstrates that pure MAO B isolated from beef liver oxidizes MPTP 38% as fast as benzylamine with a comparable Km value. Additionally, MAO A, isolated from human placenta, oxidizes MPTP to the same product at about 12% of the rate of kynuramine, again with a comparable Km value. The latter reaction is blocked by clorgyline. Both forms of MAO are progressively inactivated by MPTP by a process which follows first order kinetics. This progressive inactivation and the fact that the activity of MAO B is not significantly regenerated following gel exclusion chromatography suggest the formation of a covalent adduct with enzyme. Thus, MPTP appears to be a suicide inactivator of MAO.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine
  • Female
  • Humans
  • Isoenzymes / metabolism*
  • Kinetics
  • Mitochondria / enzymology
  • Monoamine Oxidase / metabolism*
  • Monoamine Oxidase Inhibitors*
  • Oxidation-Reduction
  • Placenta / enzymology
  • Pregnancy
  • Pyridines / metabolism*


  • Isoenzymes
  • Monoamine Oxidase Inhibitors
  • Pyridines
  • 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine
  • Monoamine Oxidase