- Interaction of tetrahydrostilbazoles with monoamine oxidase A and B
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1-Methyl-1,2,3,6-tetrahydrostilbazole (MTHS) and its analogs are oxidized by monoamine oxidase (MAO) A at slow rates comparable to that for the structurally similar neurotoxin, 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine, but the rates of oxidation by MAO B vary over a wide range depending on the structure of the analog. MAO A oxidation of all of the analogs yielded nonhyperbolic kinetic patterns, with little difference between the cis and trans isomers. In contrast MAO B showed hyperbolic kinetics and distinct stereoselectivity for the cis isomers. The corresponding pyridinium forms of trans-MTHS and its analogs were more potent inhibitors of MAO A (K(i) values between 0.3 and 5 μM) than of MAO B, for which the K(i) values varied greatly. The data suggest that the stringency of the MAO A active site for the geometry of the substrate molecule is less strict than that of MAO B. With MAO B, any substitution on the phenyl ring can lead to dramatic changes in the substrate properties which may be explained by the different orientation of substrate at the active site of the enzyme. Molecular geometry but not the effects of the substituents was shown to be an important factor in determining the effectiveness of substrate oxidation by MAO B.
- Sablin,Krueger,Singer,Bachurin,Khare,Efange,Tkachenko
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p. 151 - 157
(2007/10/02)
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- Flexible N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine analogues: Synthesis and monoamine oxidase catalyzed bioactivation
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Eighteen analogues of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were synthesized and evaluated as substrates of monoamine oxidase. In general, the flexible analogues, characterized by the presence of a methylene (or ethylene) bridge between the aryl/heteroaryl and tetrahydropyridyl moieties, were better substrates of the enzyme than the conformationally restricted MPTP. It is suggested that the increased oxidative activity of these flexible analogues reflects enhanced binding due to the ability of the C-4-aryl/heteroaryl substituent to gain access to a hydrophobic pocket within the substrate binding site.
- Efange,Michelson,Remmel,Boudreau,Dutta,Freshler
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p. 3133 - 3138
(2007/10/02)
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