title: Purification and some properties of rat liver tyrosyl-tRNA synthetase.
abstract: Rat liver cytoplasmic tyrosine:tRNA ligase (tyrosine:tRNA ligase, EC 6.1.1.1) was purified by ultracentrifugation, DEAE-cellulose chromatography and repeated phosphocellulose chromatography by more than 1500-fold. The molecular weight of the enzyme was approx. 150 000 as determined by Sephadex G-200 gel filtration. On the basis of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the enzyme consisted of two subunits, each of 68 000 daltons. We found the following Km values for the enzyme: 13 micrometer for tyrosine and 1.7 mM for ATP in the ATP:PPi exchange reaction and 13 micrometer for tyrosine, 210 micrometer for ATP and 0.14 micrometer for tRNATyr in the aminoacylation reaction. The rate of tyrosyl-tRNA synthesis was 50-fold lower than that of ATP:PPi exchange. Addition of a saturating amount of tRNA did not affect the rate of ATP:PPi exchange.
mesh_terms: D000255:Adenosine Triphosphate / Q000008:administration & dosage; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D011756:Diphosphates / Q000008:administration & dosage; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D011487:Protein Conformation; D051381:Rats; D014443:Tyrosine / Q000008:administration & dosage; D014448:Tyrosine-tRNA Ligase / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011756:Diphosphates; D014443:Tyrosine; D000255:Adenosine Triphosphate; D000604:Amino Acyl-tRNA Synthetases; D014448:Tyrosine-tRNA Ligase