title: Comparison of the enzymatic behavior of high molecular weight and free lysyl-tRNA synthetase from rat liver: kinetic analysis of lysylation of tRNA.
abstract: Lysyl-tRNA synthetase occurs in the high molecular weight form in rat liver. The high molecular weight lysyl-tRNA synthetase has been previously demonstrated to exist as multienzyme complexes of aminoacyl-tRNA synthetases. The multienzyme complexes can be dissociated by hydrophobic interaction chromatography and yield fully active, free lysyl-tRNA synthetase. The free form is found to be twice as active as the complexed form in lysylation. Bisubstrate and product inhibition kinetics of lysylation are systematically carried out for highly purified free lysyl-tRNA synthetase and the 18 S synthetase complex. Surprisingly, the two enzyme forms exhibit distinctly different kinetic patterns in bisubstrate and product inhibition kinetics under identical conditions. The 18 S synthetase complex shows kinetic patterns consistent with an ordered bi uni uni bi ping pong mechanism, while the results of free lysyl-tRNA synthetase do not. We conclude that structural organization of lysyl-tRNA synthetase beyond quaternary structure of proteins may alter the enzyme behavior.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008250:Lysine-tRNA Ligase / Q000378:metabolism*; D008433:Mathematics; D008956:Models, Chemical; D008970:Molecular Weight; D051381:Rats; D013379:Substrate Specificity
chemical_list: D000604:Amino Acyl-tRNA Synthetases; D008250:Lysine-tRNA Ligase