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Chymotrypsin is a digestive enzyme with a catalytic optimum between pH 7.8 and 8.0. However, due to the presence of gastric juice, chymotrypsin often functions in an environment of pH 5.5-7.0. The imidazole group of free histidine has a pK, of 6.0. Use the Henderson-Hasselbalch equation to determine the ratio of deprotonated to protonated His 57 imidazole moieties at pH 6.9. pH = pK₂ + log ( [His] [His+] 6.0 (VVI) Incorrect Aside from positioning, what do you think is the role of the Asp 102 residue? It allows nucleophilic attack by His 57. It raises the pK, of His 57. It protonates His 57 prior to substrate binding.

Chymotrypsin is a digestive enzyme with a catalytic optimum between pH 7.8 and 8.0. However, due to the presence of gastric juice, chymotrypsin often functions in an environment of pH 5.5-7.0. The imidazole group of free histidine has a pK, of 6.0. Use the Henderson-Hasselbalch equation to determine the ratio of deprotonated to protonated His 57 imidazole moieties at pH 6.9. pH = pK₂ + log ( [His] [His+] 6.0 (VVI) Incorrect Aside from positioning, what do you think is the role of the Asp 102 residue? It allows nucleophilic attack by His 57. It raises the pK, of His 57. It protonates His 57 prior to substrate binding.

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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To answer this question, please reference the Problem Solving Video: pH and pK, of an Amino Acid. Proteases are enzymes that cleave peptide bonds using general acid-base catalysis. General acid-base catalysis relies on a protor donor or acceptor other than water. Proteases rely on proton transfer to create strong nucleophiles from active-site amino acid residues. In the protease chymotrypsin, an active-site serine is a potent nucleophile. A nearby residue, His 57, interacts with serine to increase its reactivity. A schematic of chymotrypsin's active site illustrates the active site Ser 195 and His 57 R groups. The Asp 102 residue helps position the His 57 residue via hydrogen bonding. Asp 102 [His] [His+] His 57 6.0 -H-N Chymotrypsin is a digestive enzyme with a catalytic optimum between pH 7.8 and 8.0. However, due to the presence of gastric juice, chymotrypsin often functions in an environment of pH 5.5-7.0. Incorrect The imidazole group of free histidine has a pK₂ of 6.0. Use the Henderson-Hasselbalch equation to determine the ratio of deprotonated to protonated His 57 imidazole moieties at pH 6.9. pH = pk₂ + log Ser 195 O Identify the ways that His 57 enhances the nucleophilic power of Ser 195. acid catalyst proton acceptor base catalyst proton donor [A] [HA] Aside from positioning, what do you think is the role of the Asp 102 residue? It allows nucleophilic attack by His 57. It raises the pK, of His 57. It protonates His 57 prior to substrate binding. [His] ratio. [His+] O It decreases the
Transcribed Image Text:To answer this question, please reference the Problem Solving Video: pH and pK, of an Amino Acid. Proteases are enzymes that cleave peptide bonds using general acid-base catalysis. General acid-base catalysis relies on a protor donor or acceptor other than water. Proteases rely on proton transfer to create strong nucleophiles from active-site amino acid residues. In the protease chymotrypsin, an active-site serine is a potent nucleophile. A nearby residue, His 57, interacts with serine to increase its reactivity. A schematic of chymotrypsin's active site illustrates the active site Ser 195 and His 57 R groups. The Asp 102 residue helps position the His 57 residue via hydrogen bonding. Asp 102 [His] [His+] His 57 6.0 -H-N Chymotrypsin is a digestive enzyme with a catalytic optimum between pH 7.8 and 8.0. However, due to the presence of gastric juice, chymotrypsin often functions in an environment of pH 5.5-7.0. Incorrect The imidazole group of free histidine has a pK₂ of 6.0. Use the Henderson-Hasselbalch equation to determine the ratio of deprotonated to protonated His 57 imidazole moieties at pH 6.9. pH = pk₂ + log Ser 195 O Identify the ways that His 57 enhances the nucleophilic power of Ser 195. acid catalyst proton acceptor base catalyst proton donor [A] [HA] Aside from positioning, what do you think is the role of the Asp 102 residue? It allows nucleophilic attack by His 57. It raises the pK, of His 57. It protonates His 57 prior to substrate binding. [His] ratio. [His+] O It decreases the
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