Effect of the locus of the oxygen atom in amino ethers on the inactivation of monoamine oxidase B.

Monoamine oxidase is a flavoenzyme that catalyzes the oxidation of a variety of primary, secondary, and tertiary amines. Although primary alkylamines, such as heptylamine, and primary arylalkyl amines, such as phenylethylamine, are excellent substrates for MAO, their analogues having an electron withdrawing group near the aminomethyl methylene group (1-8) are known to inactivate the enzyme. Inactivation has been attributed to the inductive effect of the electron-withdrawing group of these analogues. To determine the extent of the proposed inductive effect of a heteroatom on MAO B inactivation, a series of oxaheptylamine analogues (9-12) were synthesized and tested as inactivators of MAO B. The analogues in which the oxygen atom is closest to the alpha-carbon (9 and 10) inactivate MAO B, but activity slowly returns with time. The analogues with the oxygen atom farther from the alpha-carbon inactivate the enzyme, but activity rapidly returns. These results support the inductive effect hypothesis for inactivation.