Many years later, in 1989, Wild, et al. revisited the idea of allosteric control of ATCase by CTP. They noted that CTP did indeed inhibit ATCase, but that the inhibition was always incomplete, even at high concentrations of CTP. They hypothesized that perhaps CTP did not act alone, but in combination with some other nucleotide. They tested the activity of ATCase in the presence of several nucleotide combinations. 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 the combination compare with the values for the nucleotides alone? Table 3: Relative specific activities for combinations of nucleotide effectors. A value greater than one indicates stimulation, a value less than one indicates inhibition. Nucleotide Effector ATP CTP GTP UTP ATP/CTP ATP/GTP ATP/UTP CTP/GTP CTP/UTP GTP/UTP KM of the nucleotide Aspartate Concentration 2.5 mM 1.86 0.31 0.57 0.95 0.70 1.98 1.96 0.41 0.05 0.66 5.0 mM 1.35 0.43 0.71 0.95 0.85 1.58 1.52 0.58 0.06 0.84

Many years later, in 1989, Wild, et al. revisited the idea of allosteric control of ATCase by CTP. They noted that CTP did indeed inhibit ATCase, but that the inhibition was always incomplete, even at high concentrations of CTP. They hypothesized that perhaps CTP did not act alone, but in combination with some other nucleotide. They tested the activity of ATCase in the presence of several nucleotide combinations. 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 the combination compare with the values for the nucleotides alone? Table 3: Relative specific activities for combinations of nucleotide effectors. A value greater than one indicates stimulation, a value less than one indicates inhibition. Nucleotide Effector ATP CTP GTP UTP ATP/CTP ATP/GTP ATP/UTP CTP/GTP CTP/UTP GTP/UTP KM of the nucleotide Aspartate Concentration 2.5 mM 1.86 0.31 0.57 0.95 0.70 1.98 1.96 0.41 0.05 0.66 5.0 mM 1.35 0.43 0.71 0.95 0.85 1.58 1.52 0.58 0.06 0.84

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter10: From Proteins To Phenotypes

Section: Chapter Questions

Problem 9QP: a. Compounds A, B, C, and D are known to be intermediates in the pathway for production of protein...

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