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Aldolase is a key enzyme in glycolysis that catalyzes the cleavage of its substrate, fructose-1,6-bisphosphate, into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The lysine and tyrosine shown are enzyme residues essential in the presented mechanism. Pi indicates inorganic phosphate.  a. Which residue, if any, is acting as a general acid in the mechanism shown above? ­­­Explain your choice. b Which of the following type(s) of catalysis is/are involved in the mechanism above?  Covalent catalysis Metal ion catalysis General acid/base catalysis none of the above c. Scientists prepared a mutant of aldolase in which tyrosine was replaced with serine. They found that the KM value for fructose-1,6-bisphosphate remained the same in the mutant as the original wild type (WT) enzyme. The value of kcat, however, decreased by a factor of 1000. Would Vmax be altered for the mutant enzyme? If so, by how much? Explain your answer. Would deltaG of the reaction be altered for the mutant enzyme? If so, in what way? Explain your answer. Would deltaG‡ be altered for the mutant enzyme? If so, in what way? Explain your answer. Draw a reaction coordinate diagram that compares the serine mutant to the WT enzyme. Put both curves on the same set of axes, being sure to label each curve as well as the axes. Your answers from (B) and (C) above should be indicated on the curves.

Aldolase is a key enzyme in glycolysis that catalyzes the cleavage of its substrate, fructose-1,6-bisphosphate, into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The lysine and tyrosine shown are enzyme residues essential in the presented mechanism. Pi indicates inorganic phosphate.  a. Which residue, if any, is acting as a general acid in the mechanism shown above? ­­­Explain your choice. b Which of the following type(s) of catalysis is/are involved in the mechanism above?  Covalent catalysis Metal ion catalysis General acid/base catalysis none of the above c. Scientists prepared a mutant of aldolase in which tyrosine was replaced with serine. They found that the KM value for fructose-1,6-bisphosphate remained the same in the mutant as the original wild type (WT) enzyme. The value of kcat, however, decreased by a factor of 1000. Would Vmax be altered for the mutant enzyme? If so, by how much? Explain your answer. Would deltaG of the reaction be altered for the mutant enzyme? If so, in what way? Explain your answer. Would deltaG‡ be altered for the mutant enzyme? If so, in what way? Explain your answer. Draw a reaction coordinate diagram that compares the serine mutant to the WT enzyme. Put both curves on the same set of axes, being sure to label each curve as well as the axes. Your answers from (B) and (C) above should be indicated on the curves.

Human Heredity: Principles and Issues (MindTap Course List)
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 14QP: If phenylalanine was not an essential amino acid, would diet therapy (the elimination of...
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  1. Aldolase is a key enzyme in glycolysis that catalyzes the cleavage of its substrate, fructose-1,6-bisphosphate, into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The lysine and tyrosine shown are enzyme residues essential in the presented mechanism. Pi indicates inorganic phosphate. 
    • a. Which residue, if any, is acting as a general acid in the mechanism shown above? ­­­Explain your choice.
    • b Which of the following type(s) of catalysis is/are involved in the mechanism above? 
      • Covalent catalysis
      • Metal ion catalysis
      • General acid/base catalysis
      • none of the above
    • c. Scientists prepared a mutant of aldolase in which tyrosine was replaced with serine. They found that the KM value for fructose-1,6-bisphosphate remained the same in the mutant as the original wild type (WT) enzyme. The value of kcat, however, decreased by a factor of 1000.
      • Would Vmax be altered for the mutant enzyme? If so, by how much? Explain your answer.
      • Would deltaG of the reaction be altered for the mutant enzyme? If so, in what way? Explain your answer.
      • Would deltaG‡ be altered for the mutant enzyme? If so, in what way? Explain your answer.
      • Draw a reaction coordinate diagram that compares the serine mutant to the WT enzyme. Put both curves on the same set of axes, being sure to label each curve as well as the axes. Your answers from (B) and (C) above should be indicated on the curves.
Lys Tyr NH2 Lys, H,0 PIO- NH2 но- -OH OH Pió Fructose-1,6-bisphosphate Lys Lys PIO- PIO- NH OH PIÓ но- H- Tyr OH Glyceraldehyde-3-phosphate OH H- PIÓ Lys Tyr Lys PiO- NH2 ENH H20 PIO- H- Туг OH H. HO Dihydroxyacetone phosphate
Transcribed Image Text:Lys Tyr NH2 Lys, H,0 PIO- NH2 но- -OH OH Pió Fructose-1,6-bisphosphate Lys Lys PIO- PIO- NH OH PIÓ но- H- Tyr OH Glyceraldehyde-3-phosphate OH H- PIÓ Lys Tyr Lys PiO- NH2 ENH H20 PIO- H- Туг OH H. HO Dihydroxyacetone phosphate
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