Aminoacyl-tRNA synthetases catalyze AMP----ADP----ATP exchange reactions, indicating labile covalent enzyme-amino-acid intermediates.
Aminoacyl-tRNA synthetases catalyze AMP----ADP----ATP exchange reactions, indicating labile covalent enzyme-amino-acid intermediates.
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氨酰-tRNA 合成酶催化 AMP----ADP----ATP 交换反应，表明共价酶-氨基酸中间体不稳定。
DOI：
10.1073/pnas.84.22.7891
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发表时间：
1987
影响因子：
11.1
通讯作者：
Zamecnik,PC
中科院分区：
文献类型：
--
作者：
Rapaport,E;Remy,P;Kleinkauf,H;Vater,J;Zamecnik,PC
氨酰-tRNA合成酶（氨基酸-tRNA连接酶，EC 6.1.1.-）以非凡的准确性催化特定氨基酸在其同源tRNA上的氨酰化。然而，最近的报告表明，这类酶可能在细胞代谢中发挥其他作用。本文显示几种氨酰-tRNA合成酶通过利用ATP的γ-磷酸转移到可能是核苷酸和相应氨基酸的混合酸酐的反应性AMP和ADP中间体来催化AMP-ADP和ADP-ATP交换反应（在没有tRNA的情况下）。AMP和ADP通过进入氨基酸活化的逆反应，与不稳定的共价氨基酸-酶中间体反应，与氨基酸产生活性中间体。已知短杆菌肽合成酶1和2通过形成氨基酸和酶的中间体硫醇-酯来活化某些氨基酸，催化具有相似特征的相同反应组。几条证据表明，这些活性是氨酰-tRNA合成酶和短杆菌肽合成酶催化的酶促反应的固有部分，而不是由于腺苷酸激酶、NDP激酶的杂质或与酶结合的低水平tRNA。共价氨基酸-酶加合物可能是其同源tRNA氨酰化的中间体。短杆菌肽合成酶的使用因此有助于阐明氨酰-tRNA合成酶催化的氨基酸活化的机理细节。
Aminoacyl-tRNA synthetases (amino acid-tRNA ligases, EC 6.1.1.-) catalyze the aminoacylation of specific amino acids onto their cognate tRNAs with extraordinary accuracy. Recent reports, however, indicate that this class of enzymes may play other roles in cellular metabolism. Several aminoacyl-tRNA synthetases are herein shown to catalyze the AMP----ADP and ADP----ATP exchange reactions (in the absence of tRNAs) by utilizing a transfer of the gamma-phosphate of ATP to reactive AMP and ADP intermediates that are probably the mixed anhydrides of the nucleotide and the corresponding amino acid. AMP and ADP produce active intermediates with amino acids by entering the back-reaction of amino acid activation, reacting with labile covalent amino acid-enzyme intermediates. Gramicidin synthetases 1 and 2, which are known to activate certain amino acids through the formation of intermediate thiol-esters of the amino acids and the enzymes, catalyze the same set of reactions with similar characteristics. Several lines of evidence suggest that these activities are an inherent part of the enzymatic reactions catalyzed by the aminoacyl-tRNA synthetases and gramicidin synthetases and are not due to impurities of adenylate kinase, NDP kinase, or low levels of tRNAs bound to the enzymes. The covalent amino acid-enzyme adducts are likely intermediates in the aminoacylation of their cognate tRNAs. The use of gramicidin synthetases has thus helped to illuminate mechanistic details of amino acid activation catalyzed by the aminoacyl-tRNA synthetases.