Mitochondrial phenylalanyl t-RNA synthetase from yeast: formation of enzyme-substrate complexes shown by heat or SH reagent inactivation.
The binding of substrates to purified mitochondrial phenylalanyl-tRNA synthetase from yeast was examined using the kinetics of heat or p-hydroxymercurybenzoate inactivation. Individually magnesium chloride and each of the substrates protect the enzyme against thermal denaturation and p-hydroxymercurybenzoate inhibition. No enzyme protection is observed with ATP alone against p-hydroxymercurybenzoate inhibition. The combinations of the various substrates induce a synergistic protection effect. Protection constants of 31 microM and 0.3 microM were found for L-Phe and mt tRNAPhe respectively, from heat inactivation studies. The inhibition of the enzyme activity by p-hydroxymercurybenzoate can be reverted by 2-mercaptoethanol or dithiothreitol.
D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D006358:Hot Temperature; D006902:Hydroxymercuribenzoates / Q000494:pharmacology; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D010652:Phenylalanine-tRNA Ligase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011489:Protein Denaturation; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013439:Sulfhydryl Reagents; D013696:Temperature
D006902:Hydroxymercuribenzoates; D007461:Iodoacetates; D013439:Sulfhydryl Reagents; C030601:4-hydroxymercuribenzoate; D000604:Amino Acyl-tRNA Synthetases; D010652:Phenylalanine-tRNA Ligase; D019807:Iodoacetic Acid