Chiral Multisubstrate Inhibitors of Dopamine -Monooxygenase: Evidence for Dual Modes of Interaction
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- 作者：Kandatege Wimalasena ; D. Shyamali Wimalasena ; Silpadipathiyalage Dharmasena ; Donovan C. Haines ; and Kevin R. Alliston
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：June 10, 1997
- 年：1997
- 卷：36
- 期：23
- 页码：7144 - 7153
- 全文大小：283K
- 年卷期：v.36,no.23(June 10, 1997)
- ISSN：1520-4995
文摘
The electronic and steric constraints of the dopamine
ddle">-monooxygenase (Dddle">M; E.C.1.14.17.1)active site were studied using a series of chiral bisubstrateinhibitors. The (R) and (S) enantiomers of5-phenyl-2-thiooxazolidone were apparent bisubstrate inhibitors forDddle">M with respect to tyramine anddioxygen, but with small enantiomeric selectivity. In contrast tothe substrate specificity of the enzyme,N-methylation of both inhibitors increased the potency without alteringthe enantiomeric selectivity. The(S) C-4-methyl substitution was more detrimental toward the inhibitionpotency compared to (R) C-4-methyl substitution for both the (R) and (S) series, which was alsoopposite of the substrate specificity ofthe enzyme. The high inhibition potency and apparent bisubstratebehavior of 3-phenyl-1,5-bisthioglutarimide (XVI), a probe designed to mimic two distinctbinding modes for the (R) and (S) inhibitors,suggested that they may interact with the enzyme by two different modesinvolving both coppers in theactive site. Direct support for the interaction of the thionegroup(s) of XVI with the reduced Dddle">Mcopper(s)is provided by the UV-vis spectroscopic studies. The completedisappearance of the characteristic UVabsorption of XVI at 336 nm in the presence ofstoichiometric amounts of reduced Dddle">M demonstratethat it could be an active site titrant for reduced Dddle">M. Theability of the enzyme to interact with theseinhibitors by more than one mode suggests that the Dddle">M active sitepossesses high steric and electronictolerance.
ddle">-monooxygenase (Dddle">M; E.C.1.14.17.1)active site were studied using a series of chiral bisubstrateinhibitors. The (R) and (S) enantiomers of5-phenyl-2-thiooxazolidone were apparent bisubstrate inhibitors forDddle">M with respect to tyramine anddioxygen, but with small enantiomeric selectivity. In contrast tothe substrate specificity of the enzyme,N-methylation of both inhibitors increased the potency without alteringthe enantiomeric selectivity. The(S) C-4-methyl substitution was more detrimental toward the inhibitionpotency compared to (R) C-4-methyl substitution for both the (R) and (S) series, which was alsoopposite of the substrate specificity ofthe enzyme. The high inhibition potency and apparent bisubstratebehavior of 3-phenyl-1,5-bisthioglutarimide (XVI), a probe designed to mimic two distinctbinding modes for the (R) and (S) inhibitors,suggested that they may interact with the enzyme by two different modesinvolving both coppers in theactive site. Direct support for the interaction of the thionegroup(s) of XVI with the reduced Dddle">Mcopper(s)is provided by the UV-vis spectroscopic studies. The completedisappearance of the characteristic UVabsorption of XVI at 336 nm in the presence ofstoichiometric amounts of reduced Dddle">M demonstratethat it could be an active site titrant for reduced Dddle">M. Theability of the enzyme to interact with theseinhibitors by more than one mode suggests that the Dddle">M active sitepossesses high steric and electronictolerance.