Comparison of the Structural Properties of the Active Site Cavities of Human and Rat Monoamine Oxidase A and B in Their Soluble and Membrane-Bound Forms
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- 作者：Anup K. Upadhyay ; Jin Wang ; Dale E. Edmondson
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：January 15, 2008
- 年：2008
- 卷：47
- 期：2
- 页码：526 - 536
- 全文大小：301K
- 年卷期：v.47,no.2(January 15, 2008)
- ISSN：1520-4995
文摘
Structural properties of the active site cavities in human and rat monoamine oxidases (MAOAand MAOB) have been studied in their detergent-purified and outer mitochondrial membrane (OMM)bound forms using a spin-labeled irreversible inhibitor (ParSL) as an active specific spin probe. ParSLhas been found to be 5-10-fold more specific for human MAOB (hMAOB) with a Ki of ca. 20 
M,compared to Ki's in the range of 100-200 M observed for other human and rat MAOs. Solventaccessibilities of the active-site-bound spin probes have been determined by studying the power saturationproperties of the spin probe EPR signals in the presence and absence of a polar paramagnetic reagentNiEDDA and by measuring the extent of spin probe reductions on treatment with excess ascorbic acid.Results presented here show that the spin probe bound to the hMAOA active site is ca. 7-8-fold moreaccessible than in hMAOB. In contrast, the spin probes covalently attached to the two rat enzyme activesites show comparable accessibilities to each other. On comparison of human versus rat enzymes, theactive-site-bound spin probes in the two rat MAOs show ca. 40% less accessibilities compared to thesame in hMAOA but ca. 4-5-fold higher accessibilities than in hMAOB active site. The present datathus suggests that the structural properties of the active site cavities in rat MAOs are significantly differentcompared to those in the two human enzymes, which correlates with the differences reported earlier inthe inhibitor specificities between human and rat MAOs.
M,compared to Ki's in the range of 100-200 M observed for other human and rat MAOs. Solventaccessibilities of the active-site-bound spin probes have been determined by studying the power saturationproperties of the spin probe EPR signals in the presence and absence of a polar paramagnetic reagentNiEDDA and by measuring the extent of spin probe reductions on treatment with excess ascorbic acid.Results presented here show that the spin probe bound to the hMAOA active site is ca. 7-8-fold moreaccessible than in hMAOB. In contrast, the spin probes covalently attached to the two rat enzyme activesites show comparable accessibilities to each other. On comparison of human versus rat enzymes, theactive-site-bound spin probes in the two rat MAOs show ca. 40% less accessibilities compared to thesame in hMAOA but ca. 4-5-fold higher accessibilities than in hMAOB active site. The present datathus suggests that the structural properties of the active site cavities in rat MAOs are significantly differentcompared to those in the two human enzymes, which correlates with the differences reported earlier inthe inhibitor specificities between human and rat MAOs.