title: Zinc-dependent synthesis of 5',5'-diadenosine tetraphosphate by sheep liver lysyl- and phenylalanyl-tRNA synthetases.
abstract: Zinc greatly stimulates the initial rate of in vitro synthesis of 5',5'-diadenosine tetraphosphate by sheep liver lysyl- and phenylalanyl-tRNMA synthetases. In the case of each enzyme, maximum stimulation of 50- to 100-fold is reached upon addition of 50 microM ZnC2 to a reaction mixture (37 degrees c, pH 7.8) containing 50 microM dithioerythritol, 150 mM KCl, 5 mM ATP, 10 mM MgCl2, 0.1 mM cognate L-aminoacid, catalytic amounts of the aminoacyl-tRNA synthetase, and unlimiting pyrophosphatase activity. This observation made with aminoacyl-tRNA synthetases of mammalian origin supports the proposal that changes in cellular free zinc ion concentration could contribute to 5',5'-diadenosine tetraphosphate variations in animal cells as a function of growth activity.
mesh_terms: D000227:Adenine Nucleotides / Q000096:biosynthesis*; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D015226:Dinucleoside Phosphates; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008250:Lysine-tRNA Ligase / Q000378:metabolism*; D010652:Phenylalanine-tRNA Ligase / Q000378:metabolism*; D012756:Sheep; D015032:Zinc / Q000494:pharmacology*
chemical_list: D000227:Adenine Nucleotides; D015226:Dinucleoside Phosphates; C020733:diadenosine tetraphosphate; D000604:Amino Acyl-tRNA Synthetases; D010652:Phenylalanine-tRNA Ligase; D008250:Lysine-tRNA Ligase; D015032:Zinc