MECHANISMS OF AMINOACYL-TRANSFER RNA-SYNTHETASES - A CRITICAL CONSIDERATION OF RECENT RESULTS
MECHANISMS OF AMINOACYL-TRANSFER RNA-SYNTHETASES - A CRITICAL CONSIDERATION OF RECENT RESULTS
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DOI：
10.1021/bi00443a001
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发表时间：
1989-08-22
期刊：
影响因子：
2.9
通讯作者：
FREIST, W
中科院分区：
文献类型：
--
作者：
FREIST, W
修订稿于 1989 年 4 月 19 日收到摘要：在过去 10 年中，人们对氨酰基-tRNA 合成酶的机制和特异性进行了深入而详细的研究。物理测量、底物化学修饰、定点诱变以及非同源氨基酸错酰化反应中动力学参数的测定提供了广泛的知识，现在对其一致性进行了严格的考虑。出现了一个共同的情况：(1) 酶在不同的测定条件下以不同的催化周期、动力学常数和特异性发挥作用。(2) 底物的化学修饰对催化的影响与测定条件的变化类似。(3) 所有酶都对 tRNA 的 2'-或 3'-位置表现出特异性。(4) 在转移前和转移后过程中实现水解校对。在大多数情况下，转校前校对是主要步骤；转印后的校对通常是微不足道的。(5) 底物的初始区分发生在两步结合过程中。对于一些研究的酶，发现最初的区分因素取决于疏水相互作用和氢键。(6)氨基酸的整体识别是在至少四个步骤的过程中实现的。目前，只能给出氨酰-tRNA 合成酶作用的粗略总体图景。
Revised Manuscript Received April 19, 1989 abstract: During the last 10 years intensive and detailed studies on mechanisms and specificities of aminoacyl-tRNA synthetases have been carried out. Physical measurements, chemical modification of substrates, site-directed mutagenesis, and determination of kinetic parameters in misacylation reactions with noncognate amino acids have provided extensive knowledge which is now considered critically for its con-sistency. A common picture emerges:(1) The enzymes work with different catalytic cycles, kinetic constants, and specificities under different assay conditions.(2) Chemical modifications of substrates can have comparable influence on catalysis as can changes in assay conditions.(3) All enzymes show a specificity for the 2'-or 3'-position of the tRNA.(4) Hydrolytic proofreading is achieved in a pre-and a posttransfer process. In most cases pretransfer proofreading is the main step; posttransfer proofreading is often marginal.(5) Initial discrimination of substrates takes place in a two-step binding process. For some investigated enzymes, initial discrimination factors were found to depend on hydrophobic interaction and hydrogen bonds.(6) The overall recognition of amino acids is achieved in a process of at least four steps. At present, only a rough overall picture of aminoacyl-tRNA synthetase action can be given.