P1，P3-双（5'-腺苷）三磷酸（Ap3A）作为哺乳动物色氨酰-tRNA合成酶的底物和产物。

P1,P3-bis(5'-adenosyl)triphosphate (Ap3A) as a substrate and a product of mammalian tryptophanyl-tRNA synthetase.

作者信息

Merkulova T, Kovaleva G, Kisselev L

机构信息

Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow.

出版信息

FEBS Lett. 1994 Aug 22;350(2-3):287-90. doi: 10.1016/0014-5793(94)00764-0.

DOI:10.1016/0014-5793(94)00764-0

PMID:8070580

Abstract

Bovine tryptophanyl-tRNA synthetase (TrpRS, E.C.6.1.1.2) is unable to catalyze in vitro formation of Ap4A in contrast to some other aminoacyl-tRNA synthetases. However, in the presence of L-tryptophan, ATP-Mg2+ and ADP the enzyme catalyzes the Ap3A synthesis via adenylate intermediate. Ap3A (not Ap4A) may serve as a substrate for TrpRS in the reaction of E.(Trp approximately AMP) formation and in the tRNA(Trp) charging. The Km value for Ap3A was higher than the Km for ATP (approx. 1.00 vs. 0.22 mM) and Vmax was 3 times lower than for ATP. The Zn(2+)-deficient enzyme catalyzes Ap3A synthesis in the absence of exogenous ADP due to ATPase activity of Zn(2+)-deprived TrpRS. The inability of mammalian TrpRS to synthesize Ap4A, might be considered as a molecular tool preventing the removal of Zn2+ due to chelation by Ap4A and therefore preserving the enzyme activity.

摘要

与其他一些氨酰 - tRNA合成酶不同，牛色氨酰 - tRNA合成酶（TrpRS，E.C.6.1.1.2）无法在体外催化Ap4A的形成。然而，在L - 色氨酸、ATP - Mg2 +和ADP存在的情况下，该酶通过腺苷酸中间体催化Ap3A的合成。在E.（色氨酸近似AMP）形成反应和tRNA（色氨酸）充电过程中，Ap3A（而非Ap4A）可作为TrpRS的底物。Ap3A的Km值高于ATP的Km值（约1.00对0.22 mM），Vmax比ATP低3倍。由于缺锌的TrpRS具有ATP酶活性，缺锌的酶在没有外源ADP的情况下催化Ap3A的合成。哺乳动物TrpRS无法合成Ap4A，可能被视为一种分子工具，可防止因Ap4A螯合而导致的Zn2 +去除，从而保持酶的活性。