title: Arginyl-tRNA synthetase from Mycobacterium smegmatis SN2: purification and kinetic mechanism.
abstract: Arginyl-tRNA synthetase [L-Arg: tRNAArg ligase (AMP forming) EC 6.1.1.19] has been purified to homogeneity from Mycobacterium smegmatis SN2. The enzyme is a monomer of molecular weight 56,000. The kinetic patterns obtained by initial velocity and product inhibition studies are consistent with a rapid equilibrium random ter ter mechanism. Polyamines stimulated the formation of arginyl-tRNA, the stimulation being more significant at sub-optimal Mg2+ concentrations. Initial velocity studies performed in the presence of sub-optimal Mg2+ and spermine also indicated that the kinetic mechanism remained sequential random. Various attempts to reveal the formation of enzyme-bound arginyl-adenylate provided no evidence for its existence. The reverse reaction, i.e., the deacylation of arginyl-tRNA, required both AMP and PPi. This observation is consistent with the mechanism proposed.
mesh_terms: D000215:Acylation; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000604:Amino Acyl-tRNA Synthetases / Q000302:isolation & purification*; D001126:Arginine-tRNA Ligase / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008970:Molecular Weight; D009161:Mycobacterium / Q000201:enzymology*; D013096:Spermine / Q000378:metabolism
chemical_list: C036687:arginyl adenylate; D013096:Spermine; D000249:Adenosine Monophosphate; D000604:Amino Acyl-tRNA Synthetases; D001126:Arginine-tRNA Ligase; D008274:Magnesium