Biological Science (7th Edition)
7th Edition
ISBN: 9780134678320
Author: Scott Freeman, Kim Quillin, Lizabeth Allison, Michael Black, Greg Podgorski, Emily Taylor, Jeff Carmichael
Publisher: PEARSON
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Textbook Question
Chapter 8, Problem 15PIAT
The functional form of PAH contains four identical active sites, but based on the amino acid sequence of the protein, only one active site can be formed. What does this imply concerning the structure of the functional enzyme?
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Chapter 8 Solutions
Biological Science (7th Edition)
Ch. 8 - 2. What is a transition state?
a. the shape...Ch. 8 - 3. How does pH affect enzyme-catalyzed...Ch. 8 - Explain how feedback inhibition regulates...Ch. 8 - 5. Explain the lock-and-key model of enzyme...Ch. 8 - If you were to expose glucose to oxygen on your...Ch. 8 - Using what you have learned about changes in Gibbs...Ch. 8 - Prob. 10TYPSSCh. 8 - 15. The functional form of PAH contains four...
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- An enzyme that catalyzes disulfide– sulfhydryl exchange reactions, called protein disulfide isomerase (PDI), has been isolated. PDI rapidly converts inactive scrambled ribonuclease into enzymatically active ribonuclease. In contrast, insulin is rapidly inactivated by PDI. What does this important observation imply about the relation between the amino acid sequence of insulin and its threedimensional structure?arrow_forwardTwo isoforms of an enzyme were discovered; isoform-1 produces a hormone that causes muscle spasms and isoform-2 makes a different hormone (from the same substrate) that lowers cholesterol levels. a) What strategy would you employ as a medicinal chemist to develop a drug that prevents muscle spasms without raising cholesterol levels? The active sites of isoform-1 and -2 are the same except isoform-1 has a cysteine residue and isoform-2 has a phenylalanine residue at that same position. b) What two approaches would you take for designing a muscle spasm drug without a cholesterol level increase side effect?arrow_forwardSome of the following four amino acids : alanine, arginine, histidine, aspartic acid would provide a side chain for acid-base catalysis at physiological pH (assume pK of each amino acid is equal to pK value for the free amino acid in solution). Explain for each amino acid how and why each would or would not provide the side chain residue to support acid-base catalysis at physiological pH.arrow_forward
- Chymotrypsin is a pH dependent protein. Enzymatic activity is the greatest between pH=7.0 to pH=8.5. Which residue in the active site would be most affected by decreasing the pH below this range? Explain.arrow_forwardWhy do structural analogs of the transition-state intermediate of an enzyme inhibit the enzyme competitively and with low Ki values (binds tightly)?arrow_forwardSnake venom contains many hydrolase enzymes, including several serine proteases. One such protease (present in high concentrations in snake venom) mimics the action of thrombin to activate fibrin. The venom protease cleaves peptide bonds with a specificity for basic, positively charged amino acids. This enzyme is incubated with a substrate peptide with the sequence SNPDCKVALYMTW. Draw a mechanism for the peptide hydrolysis of this specific peptide catalyzed by this snake venom protease. Include the structure of the active site amino acids of the enzyme and the substrate peptide group (including the full structure of the 2 specific amino acids that contribute to the scissile peptide group in the substrate) in your mechanism. Use the curved arrow convention to illustrate the flow of electrons.arrow_forward
- The pKa for histidine is pKa = 6.1 while that for cysteine is pKa = 8.0 2. Assume that both histidine and cysteine are catalytic groups for a particular enzyme. Assume also that the side chain of cysteine must be in the deprotonated form. Estimate the pH at which the catalytic activity of this enzyme is the maximum and sketch a pH-activity graph.arrow_forwardGlobular proteins with multiple disulfide bonds must be heated longer and at higher temperature to denature them. Bovinepancreatic trypsin inhibitor (BPTI), having 58 amino acids in a single chain and 3 disulfide linkages, loses its catalytic activity whenheated at nearly 90°C for 5-10 minutes. Explain the molecular basis of this observed thermal property of BPTI relative to the nativestructure and function of the protein. please do not copy from other answers herearrow_forwardCarboxypeptidase Y (CPY) contains ten cysteine residues that form five disulfide bonds in the native structure of CPY. Suppose CPY is reduced and unfolded in urea.Part AIf the reduced unfolded protein were oxidized prior to the removal of the urea, what fraction of the resulting mixture would you expect to possess native disulfide bonds?Express your answer using three significant figures.arrow_forward
- The active site of an enzyme that uses a general acid-base catalytic mechanism contains a Glu and an Asp residue (both of which are essential for catalysis) with pKa values of 5.9 and 4.5, respectively. If the enzyme is found in the lysosome (pH = 5.2), which residue will act as the general acid and which will act as the general base during the initial steps of the reaction?arrow_forwardWhen performing his experiments on protein refolding, Christian Anfinsen obtained a quite different result when reduced ribonuclease was reoxidized while it was still in 8 M urea and the preparation was then dialyzed to remove the urea. Ribonuclease reoxidized in this way had only 1% of the enzymatic activity of the native protein. Why were the outcomes so different when reduced ribonuclease was reoxidized in the presence and absence of urea?arrow_forwardThis image is showing the conformations of ubiquitin superimposed. What do the structures in this figure tell us about the dynamics of enzymes? Discuss the limitations of crystal structures in the analysis of proteins. What are the benefits? What are the advantages of NMR structures?arrow_forward
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