1 ).Which of the following accurately describes substrate specificity for serine proteases? A.The binding cleft B.Mg2+ metal activated enzyme C.The catalytic triad D.Facilitates redox chemistry E.Stabilizes the transition state 2). Which of the following amino acid residues would not provide a side chain for acid-base catalysis at physiological pH? select all that apply leucine aspartic acid histidine lysine

1 ).Which of the following accurately describes substrate specificity for serine proteases? A.The binding cleft B.Mg2+ metal activated enzyme C.The catalytic triad D.Facilitates redox chemistry E.Stabilizes the transition state 2). Which of the following amino acid residues would not provide a side chain for acid-base catalysis at physiological pH? select all that apply leucine aspartic acid histidine lysine

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter4: Cells

Section: Chapter Questions

Problem 1ITD

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An active site of a hypothetical serine protease with a peptide substrate bound is shown below: This serine protease has 3 specificity pockets (S1, S2, S1') as shown in the figure above. S1 pocket has a glutamic acid in the bottom, the S2 pocket is small and hydrophobic, and the S1' pocket is deep and hydrophobic. Based on this information you can conclude that R1 is most likely side chain of a. Asp b. Lys c. Lle d. Gly e. Phe
Using the catalytic mechanism of serine proteases, draw and label a reaction coordinate diagram/graph of the chymotrypsin-catalyzed hydrolysis of a peptide bond.
Which of the following best explains why enzyme catalysis is affected by a change in pH? A. Change in pH alters ionization states of serine in the active site involved in nucleophilic catalysis B. The ionization states of his, asp and glu involved in acid/base catalysis are altered with change in pH C. Change in pH alters ionization states of contact amino acids in the active site D. All enzymes have optimum pH
complete the following mechanism showing the cleavge of the peptide bond for the following cysteine protease reaction. you only need a catalytic dyad for cystein proteases because the pKa of cysteine is low enough (8) and close enough to the pH of 7.4 that is can easily be deprotonated by histidine.
The following data describe the catalysis of cleavage of peptide bonds in small peptides by the enzyme UTSAse (the arrow indicates the peptide bond cleaved in each case). Substrate Km(mM) kcat(s-1) PAPA↓G 4.0 26 PAPA↓A 1.5 37 PAPA↓F 0.64 18 what features of amino acid sequence dictate the specificity of the proteolytic cleavage? Large hydrophilic R-groups Large hydrophobic R-groups Neutral R-groups Small hydrophilic R-groups Large hydrophobic R-groups Negatively charged R-groups Positively charged R-groups
3CLpro is a cysteine protease, which are among the most common proteases in biochemistry, however they are a structurally diverse family of enzymes especially in the organization of the active site amino acids. A group of scientists have reported a potential drug molecule based on a binding study using circular dichroism. They report that the molecule binds to the active site. Can the experiment support the claims, why or why not? Which techniques might be used to support this claim?
Which of the following statements is true? a. Plotting the rate of facilitated transport against substrates gives a sigmoidal curve b. Facilitated carrier proteins can be saturated by substrates c. Both A and B d. Neither A nor B The catalytic triad of chymotrypsin and other serine proteases consists of _________ A. three subunits of the enzyme. B. three amino acid residues close enough in space to make serine a strong nucleophile. C. three enzymes with very similar structural features. D. three amino acid residues adjacent in the primary structure which act to make serine a strong nucleophile. E. None of the above.
In the first step of the aldolase reaction, an active site Lys229 residue, with its side chain amino group in the deprotonated state, acts as a nucleophile and attacks the carbonyl C2 carbon of fructose 1,6-bisphosphate to form a Schiff base (boxed in the scheme). Since the pKa of the Lys side chain amino group in free solution is ~10.5, the pKa of Lys229 side chain must have been perturbed to a (higher lower) value for the enzyme to be active at neutral pH. the answer should include sufficient details, including the definition of pKa.
The steps of the chymotrypsin mechanisms are listed below (1-7). Put the steps of chymotrypsin mechanism in the correct order. Figure representing chymotrypsin mechanism is given for reference. a.The portion (N-terminal end) of original substrate with the new C terminus diffuses away b. Substrate binding c. His 57 catalyzes removal of H from Ser 195 hydroxyl; Ser 195’s nucleophilic O attacks carbonyl C of substrate; tetrahedral intermediate is formed d. Water binding; water is deprotonated by His 57; resulting OH nucleophilically attacks carbonyl of remaining substrate; tetrahedral intermediate is formed e. His 57 donates H to N of…
Bovine chymotrypsin is a serine protease. The enzyme is structurally stable over the pH range of 4.0 – 10.0. It exhibits optimum protease activity in the pH range of 7.5 – 9.0, but its protease activity is strongly inhibited at pH < 6.0. Based on your knowledge of serine protease mechanisms, how would you explain this effect of pH on chymotrypsin’s mechanism of catalysis?
Shown below is a proposed mechanism for the cleavage of sialic acid by the viral enzyme neuraminidase. The kcat for the wild-type enzyme at pH =6.15, 37 °C is 26.8 s-1.(a) Describe the roles of the following amino acids in the catalytic mechanism: Glu117, Tyr409, and Asp149. List all of the following that apply:general acid/base catalysis (GABC), covalent catalysis, electrostaticstabilization of transition state.(b) Based on the information shown in the scheme, would you expect mutation of Glu 117 to Ala to have a greater effect on KM or kcat?(c) For the R374N mutant at pH = 6.15, 37 °C, kcat is 0.020 s-1, and KMis relatively unaffected. Based on this result, it seems that R374 is morecritical for catalysis than for substrate binding. Explain how R374 stabilizesthe reaction transition state more than the substrate (i.e., what feature of this reaction would explain tighter binding to the transition state vs. substrate?).
Consider, for example, that a particular serine residue is phosphorylated to activate the protein. In the lab, a similar effect is achieved by mutating this residue to either a D (aspartic acid) or E (glutamic acid). What could be the reason?