INTERACTIONS OF AMINOACYL-TRANSFER RNA-SYNTHETASES IN HIGH-MOLECULAR-WEIGHT MULTIENZYME COMPLEXES FROM RAT-LIVER
INTERACTIONS OF AMINOACYL-TRANSFER RNA-SYNTHETASES IN HIGH-MOLECULAR-WEIGHT MULTIENZYME COMPLEXES FROM RAT-LIVER
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DOI：
10.1016/0167-4838(85)90239-0
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发表时间：
1985-01-01
期刊：
影响因子：
--
通讯作者：
YANG, DCH
中科院分区：
文献类型：
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作者：
DANG, CV;FERGUSON, B;YANG, DCH
通过检测酶的催化活性和失活动力学，研究了在同一大鼠肝多酶复合物中发生的Arg-、Ile-、Leu-、Lys-和Met-tRNA合成酶的功能相互作用。的米氏常数的氨基酸，ATP和tRNA的解离的氨酰-tRNA合成酶是没有显着不同的高分子量的多酶复合物，除了在少数情况下，解离的酶的Km值高于那些高分子量的形式。单个氨酰-tRNA合成酶的最大氨酰化速度不受同一多酶复合物中另一种合成酶同时氨酰化的影响。位点特异性抗坏血酸氧化修饰和非特异性热灭活的合成酶在纯化的大鼠肝18 S合成酶复合物进行检查。赖氨酸-和精氨酸-tRNA合成酶在两个失活过程中显示出显着的平行时间过程。Leu-和Met-tRNA合成酶在热活化和可能的氧化失活中也显示出平行的动力学。Ile-tRNA合成酶在这两个过程中几乎没有失活。赖氨酸和精氨酸tRNA合成酶的氧化失活可以通过加入二硫苏糖醇逆转。显然，同一高分子量复合物中的合成酶独立地催化氨酰化反应;多酶复合物中某些合成酶的稳定性是耦合的。特别地，Arg-tRNA合成酶的稳定性明显取决于其与完全活性的Lys-tRNA合成酶的结合。
The functional interaction of Arg-, Ile-, Leu-, Lys- and Met-tRNA synthetases occurring within the same rat liver multienzyme complex are investigated by examining the enzymes catalytic activities and inactivation kinetics. The Michaelis constants for amino acids, ATP and tRNA of the dissociated aminoacyl-tRNA synthetases are not significantly different from those of the high MW multienzyme complex, except in a few cases where the Km values of the dissociated enzymes are higher than those of the high-MW form. The maximal aminoacylation velocities of the individual aminoacyl-tRNA synthetases are not affected by the presence of simultaneous aminoacylation by another synthetase occurring within the same multienzyme complex. Site-specific oxidative modification by ascorbate and nonspecific thermal inactivation of synthetases in the purified rat liver 18 S synthetase complex are examined. Lys- and Arg-tRNA synthetases show remarkably parallel time-courses in both inactivation processes. Leu- and Met-tRNA synthetases also show parallel kinetics in thermal activation and possibly oxidative inactivation. Ile-tRNA synthetase shows little inactivation in either process. The oxidative inactivation of Lys- and Arg-tRNA synthetases can be reversed by addition of dithiothreitol. Apparently, synthetases within the same high-MW complex catalyze aminoacylation reactions independently; the stabilities of some of the synthetases in the multienzyme complex are coupled. In particular, the stability of Arg-tRNA synthetase depends appreciably on its association with fully active Lys-tRNA synthetase.