Inactivation of monoamine oxidase B by benzyl 1-(aminomethyl) cyclopropane-1-carboxylate.
Monoamine oxidase (MAO) is a flavoenzyme that catalyzes the oxidation of various biogenic and xenobiotic amines. Benzyl 1-(aminomethyl)cyclopropane-1-carboxylate (1) was designed as a diactivated cyclopropane mechanism-based inactivator of MAO (Silverman, R.B.: Ding, C.Z.; Borrillo, J.L.; Chang, J.T.J. Am. Chem. Soc. 1993, 115, 2982). [1,1-2H2]-1 exhibits a deuterium isotope effect of 4.5 on inactivation, but in D2O the isotope effect is only 2.3. [1-3H]-1 and [1-14C]-1 were synthesized; upon inactivation of MAO, 1.1 and 2.0 equiv of radioactivity, respectively, are incorporated into the enzyme. Tritium as 3H2O, is released during inactivation with [1-3H]-1. The flavin absorption spectrum changes from that of oxidized to that of reduced flavin after inactivation; denaturation of the inactivated enzyme shows a reduced flavin spectrum, suggesting the formation of a modified flavin. Tryptic digestion of the enzyme labeled with [1-3H]-1 or [1-14C]-1, followed by HPLC analysis, monitoring at 310 nm [corrected] (flavin), shows that the radioactivity comigrates with the 310 nm [corrected] absorptions. The metabolites that are generated during inactivation are benzyl 1-formylcyclopropane-1-carboxylate, benzyl alcohol, and 1-formylcyclopropane-1-carboxylic acid; no ring-cleaved products were detected. The partition ratio, as determined from the ratio of nonamines to enzyme, is 110. These results are rationalized in terms of a single-electron transfer mechanism leading to the imine of benzyl 1-formylcyclopropane-1-carboxylate, which alkylates the flavin coenzyme.
Silverman
R B
RB
Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
Lu
X
X
Blomquist
G D
GD
Ding
C Z
CZ
Yang
S
S
D000596:Amino Acids / Q000737:chemistry / Q000494:pharmacology*; D000598:Amino Acids, Cyclic; D009682:Magnetic Resonance Spectroscopy; D008996:Monoamine Oxidase Inhibitors / Q000737:chemistry / Q000494:pharmacology*
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D008996:Monoamine Oxidase Inhibitors; C105910:benzyl 1-(aminomethyl)cyclopropane-1-carboxylate