Many years later, in 1989, Wild, et al. revisited the idea of allosteric control of ATCase by CTP. Theynoted that CTP did indeed inhibit ATCase, but that the inhibition was always incomplete, even at highconcentrations of CTP. They hypothesized that perhaps CTP did not act alone, but in combinationwith some other nucleotide. They tested the activity of ATCase in the presence of several nucleotidecombinations. The results are shown in Table 3.a. What combination gives the most effective inhibition?b. What is the physiological significance of this combination?c. Revise Figure 1 to include this new information.d.Redraw Figure 2 to include this new information. How does thecombination compare with the values for the nucleotides alone?Table 3: Relative specific activities for combinations of nucleotide effectors. A value greater than oneindicates stimulation, a value less than one indicates inhibition.Nucleotide EffectorATPCTPGTPUTPATP/CTPATP/GTPATP/UTPCTP/GTPCTP/UTPGTP/UTPKM of the nucleotideAspartate Concentration2.5 mM1.860.310.570.950.701.981.960.410.050.665.0 MM1.350.430.710.950.851.581.520.580.060.84 HCO₂ + Glutamine + ATPCarbamoyl phosphate + AspartateFigure 1: Pyrimidine synthetic pathway.51Velocity, activity units/mgprotein23AT Case0N-carbamoylaspartate51520Aspartate concentration, mMControl With CTP - With ATP1025Figure 2: Kinetics of ATCase in the presence of ATP andCTP (based on Gerhart and Pardee, 1962).UMPUTP-CTP

Here we are considering the allosteric enzyme ATCase (Aspartate transcarbamoylase), whose kinetics…

Answered: Many years later, in 1989, Wild, et al.…

Biochemistry

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Chapter1: Biochemistry: An Evolving Science

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The authors state: "Properties of the single mutants K557R, D591V and K617A, a double mutant, D591V/K617A, and a triple mutant, K557R/D591V/K617A, were evaluated to find an allosteric binding site for citrate." The numbers between the letters represent the residue number altered. The letter in front was the wild type and the letter afterwards is the mutant. How would the the triple mutations K557R and D591V and K617A alter the overall protein? O lower the # of charges, increase the pl O increase the # of charges, increase the pl O lower the # of charges, lower the pl O lower the # of charges, increase the pl O no change in the # of charges, increase the pl O no change in the # of charges, lower the pl
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