Harnett S P, Lowe G, Tansley G
Biochemistry. 1985 Jun 4;24(12):2908-15. doi: 10.1021/bi00333a014.
The activation of L-phenylalanine by yeast phenylalanyl-tRNA synthetase using adenosine 5'-[(S)-alpha-17O,alpha,alpha-18O2]triphosphate is shown to proceed with inversion of configuration at P alpha of ATP. This observation taken together with the lack of positional isotope exchange when adenosine 5'-[beta,beta-18O2]triphosphate is incubated with the enzyme in the absence of phenylalanine and in the presence of the competitive inhibitor phenylalaninol indicates that activation of phenylalanine occurs by a direct "in-line" adenylyl-transfer reaction. In the presence of Zn2+, yeast phenylalanyl-tRNA synthetase also catalyzes the phenylalanine-dependent hydrolysis of ATP to AMP and the synthesis of P1,P4-bis(5'-adenosyl) tetraphosphate (Ap4A). With adenosine 5'-[(S)-alpha-17O,alpha,alpha-18O2]triphosphate, the formation of AMP and Ap4A is shown to occur with inversion and retention of configuration, respectively. It is concluded that phenylalanyl adenylate is an intermediate in both processes, Zn2+ promoting AMP formation by hydrolytic cleavage of the C-O bond and Ap4A formation by displacement at phosphorus of phenylalanine by ATP.
酵母苯丙氨酰 - tRNA合成酶利用腺苷5'-[(S)-α - 17O,α,α - 18O2]三磷酸对L - 苯丙氨酸的激活作用显示，在ATP的Pα处构型发生翻转。这一观察结果，再加上当腺苷5'-[β,β - 18O2]三磷酸在无苯丙氨酸且存在竞争性抑制剂苯丙氨醇的情况下与该酶一起温育时缺乏位置同位素交换，表明苯丙氨酸的激活是通过直接的“直线型”腺苷酰转移反应发生的。在Zn2+存在的情况下，酵母苯丙氨酰 - tRNA合成酶还催化ATP在苯丙氨酸依赖下水解为AMP以及合成P1,P4 - 双(5'-腺苷基)四磷酸(Ap4A)。对于腺苷5'-[(S)-α - 17O,α,α - 18O2]三磷酸，AMP和Ap4A的形成分别显示为构型翻转和构型保留。得出的结论是，苯丙氨酰腺苷酸是这两个过程的中间体，Zn2+通过水解断裂C - O键促进AMP的形成，以及通过ATP对苯丙氨酸磷原子的取代促进Ap4A的形成。
