Open AccessDimeric glutamyl‐tRNA synthetases from wheat Kinetic properties and functional structures
Author(s) -
THOMES Jean Claude,
RATINAUD Marie Hélène,
JULIEN Raymond
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07676.x
Subject(s) - aminoacylation , transfer rna , enzyme , chemistry , dissociation constant , glutamic acid , biochemistry , aminoacyl trna synthetase , dissociation (chemistry) , michaelis–menten kinetics , amino acid , kinetics , stereochemistry , enzyme assay , rna , organic chemistry , physics , receptor , quantum mechanics , gene
1 The Michaelis constants in the tRNA aminoacylation reaction have been studied for the three dimeric glutamyl‐tRNA synthetases C, P and E. The values were found to be: for tRNA, 0.20 μM, 0.20 μM, 0.20 μM and 0.44 μM; for glutamic acid, 10 μM, 83 μM and 83 μM; for MgATP, 0.46 mM, 0.38 mM and 0.26 mM. MgATP concentrations higher than 2 mM induce pronounced inhibition. 2 The presence of the cognate tRNA is required for [ 32 P]PP i ‐ATP isotopic exchange. In the absence of tRNA no hyperbolic saturation of the enzymes by glutamic acid occurs in our experimental conditions. 3 Analysis of the enzymic activity as a function of enzyme concentration leads to the conclusion that the active forms are dimers which are in equilibrium with inactive monomers. The values of the dissociation constants K d were found to be 43 nM, 53 nM and 87 nM for glutamyl‐tRNA synthetases C, P and E respectively.