Rabbit aorta glutathione S-transferases and their role in bioactivation of trinitroglycerin.
Rabbit aorta glutathione S-transferases and their role in bioactivation of trinitroglycerin.
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兔主动脉谷胱甘肽 S-转移酶及其在三硝化甘油生物活化中的作用。
DOI：
10.1006/taap.1996.0234
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Awasthi,YC
中科院分区：
文献类型：
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作者：
Singhal,SS;Piper,JT;Srivastava,SK;Chaubey,M;Bandorowicz-Pikula,J;Awasthi,S;Awasthi,YC
硝酸甘油(GTN)是一种广泛用于治疗心绞痛的药物，其药理作用被认为是通过在其生物转化过程中释放一氧化氮(NO)来实现的。由于谷胱甘肽转移酶(GST)可以利用GTN作为底物，GST抑制剂可以减弱GTN引起的兔主动脉松弛，因此这些酶参与了GTN在兔主动脉中的生物激活。由于GST是一种多功能酶，哺乳动物组织中存在多种具有不同底物选择性的GST同工酶，因此需要确定特定的GST同工酶在兔主动脉GTN生物激活中的作用。因此，在本研究中，我们从兔主动脉中纯化和鉴定了GST同工酶，并评价了它们在GTN生物转化中的可能作用。结果表明，兔主动脉中含有三种GST同工酶，其等电点分别为9.4、7.7和5.4。结构、免疫学和动力学研究表明，GST9.4、GST7.7和GST5.4分别属于α-，π-和μ-类。这些酶在兔主动脉中的相对丰度为α>；π>；μ。α和μ同工酶对谷氨酸氨基转移酶的活性相近(分别为0.71U/mg和0.86U/mg)，而π同工酶对谷氨酸氨基转移酶的活性较低。μ级和α级GST对Gtn的催化效率kcat/Km相似，但这些活性分别被乙氰酸、其谷胱甘肽结合物、溴磺化邻苯二甲酸和血红素所抑制。这些结果提示，在兔主动脉中，GSTs可能参与了GTN的生物活性，而且由于其丰度较高，α类GSTs可能比μ类GSTs对GTN的药理作用更重要。不同抑制剂抑制GTN的动力学结果表明，血红素可能是一种有效的抑制GST同工酶在GTN生物活性中的作用的抑制剂。
The pharmacological action of glyceryl trinitrate (GTN), a widely used drug for the treatment of angina pectoris, is thought to be mediated through release of nitric oxide (NO) during its biotransformation. Since glutathioneS-transferases (GST) can utilize GTN as substrate and GST inhibitors can attenuate GTN-induced relaxation of rabbit aortain vitroit has been suggested that these enzymes are involved in the bioactivation of GTN in rabbit aorta. Because GSTs are multifunctional enzymes and a multitude of GST isozymes with varying substrate preferences are present in mammalian tissues, the role of specific GST isozymes in bioactivation of GTN in rabbit aorta needs to be established. Therefore, during the present studies we have purified and characterized GST isozymes from rabbit aorta and evaluated their possible roles in the biotransformation of GTN. The results of these studies showed that rabbit aorta contained three GST isozymes having pI values of 9.4, 7.7, and 5.4. Structural, immunological, and kinetic studies showed that GST 9.4, GST 7.7, and GST 5.4 belonged to the α-, π-, and μ-classes, respectively. The relative abundance of these enzymes in rabbit aorta was α > π > μ. The α- and μ-class GST isozymes had similar activities toward GTN (0.71 U/mg and 0.86 U/mg, respectively) while the π-class GST showed much lower activity toward GTN. The catalytic efficiencykcat/Kmof the μ- and α-class GSTs toward GTN were similar but these activities were differentially inhibited by ethacrynic acid, its GSH conjugate, bromosulfophthalein (BSP), and hematin. These results suggest that in rabbit aorta GSTs may be involved in bioactivation of GTN, and because of their higher abundance the α-class GSTs may be more important for the pharmacological effects of GTN than the μ-class GSTs. The results on kinetics of inhibition by various inhibitors suggest that hematin may be an effective inhibitor to delineate the role of specific GST isozymes in the bioactivation of GTN.