title: [Kinetic model describing the action of tryptophanyl-tRNA-synthetase].
abstract: Reaction rates for ATP-PPi isotope exchange (vex) and tryptophanyl-tRNA formation (vaa) catalysed concomitantly in one incubation mixture by beef pancreas tryptophanyl-tRNA synthetase (trsase) have been examined as a function of substrate concentrations. Comparison of the vex/vaa ratio found experimentally with the ratio predicted theoretically conforms the mechanism suggested earlier and permits to describe it in more detail. I. At least two reaction routes exist in which an ATP-PP: exchange is allowed. These routes are interconnected with each other via the stage at which tRNA binds to the enzyme. 2. In both these routes the low molecular weight substrates bind with enzyme in the order ATP first, tryptophan second. 3. Enzyme-aminoacyladenylate complex is an intermediate in the reaction of aminoacyl-tRNA formation. Pyrophosphate is detached from the enzyme prior to tRNA. 4. The enzyme releases AMP and tryptophanyl-tRNA in a random fashion. All the aformentioned properties are common both for trigger mechanism and Yarus-Berg mechanism which up to now were considered in literature independently.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D007700:Kinetics; D008954:Models, Biological; D010179:Pancreas / Q000201:enzymology; D014369:Tryptophan-tRNA Ligase / Q000378:metabolism*
chemical_list: D000604:Amino Acyl-tRNA Synthetases; D014369:Tryptophan-tRNA Ligase
vernacular_title: Kineticheskaia model', opisyvaiushchaia deĭstvie triptofanil-tRNK-sintetazy.