Deuterium isotope effects for the oxidation of 1-methyl-3-phenyl-3-pyrrolinyl analogues by monoamine oxidase B

Anél Pretorius, Modupe O. Ogunrombi, Gisella Terre'Blanche, Neal Castagnoli, Jacobus J. Bergh, Jacobus P. Petzer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The parkinsonian inducing agent, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is a cyclic tertiary allylamine exhibiting good monoamine oxidase B (MAO-B) substrate properties. MAO-B catalyzes the ring α-carbon 2-electron bioactivation of MPTP to yield the 1-methyl-4-phenyl-2,3-dihydropyridinium species (MPDP+). The corresponding 5-membered ring MPTP analogue, 1-methyl-3-phenyl-3-pyrroline, also undergoes MAO-B-catalyzed oxidation to give the 2-electron oxidation product, 1-methyl-3-phenylpyrrole. Here we report the kinetic deuterium isotope effects on Vmax and Vmax/Km for the steady-state oxidation of 1-methyl-3-phenyl-3-pyrroline and 1-methyl-3-(4-fluorophenyl)-3-pyrroline by baboon liver MAO-B, using the corresponding pyrroline-2,2,4,5,5-d5 analogues as the deuterated substrates. The apparent isotope effects for the two substrates were 4.29 and 3.98 on Vmax, while the isotope effects on Vmax/Km were found to be 5.71 and 3.37, respectively. The values reported for the oxidation of MPTP by bovine liver MAO-B with MPTP-6,6-d2, as deuterated substrate, are D(Vmax) = 3.55; D(Vmax/Km) = 8.01. We conclude that the mechanism of the MAO-B-catalyzed oxidation of pyrrolinyl substrates is similar to that of the tetrahydropyridinyl substrates and that a carbon-hydrogen bond cleavage step is, at least partially, rate determining.

Original languageEnglish
Pages (from-to)8813-8817
Number of pages5
JournalBioorganic and Medicinal Chemistry
Issue number19
Publication statusPublished - 1 Oct 2008
Externally publishedYes


  • 1-Methyl-3-phenyl-3-pyrroline
  • Kinetic isotope effect
  • MPTP
  • Monoamine oxidase B


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