Lõvgren T N, Heinonen J, Loftfield R B
J Biol Chem. 1975 May 25;250(10):3854-60.
Isoleucyl adenylate bound to isoleucine:tRNA ligase of Escherichia coli (EC 6.1.1.5; isoleucyl-tRNA synthetase) transfers the isoleucine moiety to tRNA-Ile-E. coli with a half-time of about 35 s at 0 degrees and pH 7.6 in the presence of spermine or Mg2+. If a limited amount of tRNA-Ile is supplied to a mixture of free enzyme and enzyme-bound [14c]isoleucyl adenylate in a medium containing spermine, ATP, and [3H]isoleucine, almost none of the resultant isoleucyl tRNA is derived from preformed enzyme-bound [14C]isoleucyl adenylate. Almost all of the isoleucyl tRNA formed results directly from reaction of free enzyme, ATP, and isoleucine with tRNA. Similar but less clearcut results are obtained when Mg2+ is substituted for spermine. We conclude that isoleucyl adenylate bound to isoleucine:tRNA ligase is not a significant intermediate in the synthesis of isoleucyl tRNA under these conditions.
与异亮氨酸 - tRNA连接酶（大肠杆菌的EC 6.1.1.5；异亮氨酰 - tRNA合成酶）结合的异亮氨酰腺苷酸，在0℃、pH 7.6且存在精胺或Mg2+的情况下，以约35秒的半衰期将异亮氨酸部分转移至大肠杆菌的tRNA - Ile。如果在含有精胺、ATP和[3H]异亮氨酸的培养基中，向游离酶和与酶结合的[14C]异亮氨酰腺苷酸的混合物中提供有限量的tRNA - Ile，几乎没有所得的异亮氨酰tRNA源自预先形成的与酶结合的[14C]异亮氨酰腺苷酸。几乎所有形成的异亮氨酰tRNA都是游离酶、ATP和异亮氨酸与tRNA直接反应的结果。当用Mg2+替代精胺时，会得到类似但不太明确的结果。我们得出结论，在这些条件下，与异亮氨酸 - tRNA连接酶结合的异亮氨酰腺苷酸在异亮氨酰tRNA的合成中不是一个重要的中间体。
