MECHANISMS OF TOXICITY OF 3'-AZIDO-3'-DEOXYTHYMIDINE
MECHANISMS OF TOXICITY OF 3'-AZIDO-3'-DEOXYTHYMIDINE
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DOI：
10.1016/0006-2952(94)90564-9
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发表时间：
1994-10-07
影响因子：
5.8
通讯作者：
SIMPSON, MV
中科院分区：
文献类型：
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作者：
BARILE, M;VALENTI, D;SIMPSON, MV
本实验室最近的实验表明，3‘-叠氮-3’-脱氧胸苷(AZT)对氧化磷酸化的抑制作用除通过抑制线粒体DNA复制而起作用外，还可能直接发生。我们报道了AZT对腺苷酸激酶的影响，腺苷酸激酶是氧化磷酸化的关键酶。AZT降低了兔肌腺苷酸激酶的芳香族残基荧光，表明AZT与该酶结合。在作为对照研究的其他三种酶中，AZT只与那些具有ATP/ADP结合位点的酶结合。与ATP、ADP、AMP和AZT对照的脱氧胸腺嘧啶核苷相比，AZT在15mU M浓度下对荧光猝灭的作用更强。AZT强烈抑制腺苷酸激酶的合成(K-I，8µM)，其抑制作用为部分竞争性，而脱氧胸腺嘧啶核苷的抑制作用较弱(K-I，90µM)。在ADP合成方向上测量时，AZT在10 mU M以下的浓度下没有表现出任何抑制作用。在分离的完整大鼠肝线粒体上进行的双向酶活性实验证实了分离的酶结果。这些线粒体的呼吸控制不受AZT的影响。AZT与ATP/ADP结合位点亲和力的发现可能为研究AZT的毒性开辟新的途径。
Recent experiments from our laboratory have indicated that the inhibitory effect of 3'-azido-3'-deoxythymidine (AZT) on oxidative phosphorylation may occur directly in addition to being brought about by its inhibition of mtDNA replication. We report here studies on the effect of AZT on adenylate kinase, an enzyme crucial to oxidative phosphorylation. AZT decreased the aromatic residues fluorescence of rabbit muscle adenylate kinase, indicating binding of AZT to the enzyme. Of three other enzymes studied as controls, AZT bound only to those that possessed ATP/ADP binding sites. Up to concentrations of 15 mu M, AZT was a more potent effector of fluorescence quenching than were ATP, ADP, AMP, and the AZT control, deoxythymidine. AZT strongly inhibited adenylate kinase in the direction of ATP synthesis (K-i, 8 mu M), the inhibition being of the partial competitive type, whereas deoxythymidine inhibition, also partially competitive, was much weaker (K-i 90 mu M). When measured in the direction of ADP synthesis, AZT failed to demonstrate any inhibition at concentrations up to 10 mu M. Experiments on isolated intact rat Liver mitochondria with the enzyme activity measured in both directions confirmed the isolated enzyme results. Respiratory control by these mitochondria was not affected by AZT. The finding of AZT affinity for ATP/ADP binding sites may open new avenues of approach to the study of AZT toxicity.