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Which feature of the enzyme active site do you expect to increase

Which feature of the enzyme active site do you expect to increase

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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b. The C-2 atom in 2-phosphoglycerate is not acidic in solution, i.e. it does not have a tendency to lose its proton (colored blue above). However, in the active site of enolase, C-2 has a lowered pKa and is acidic enough that Lys45 can extract its proton. Which feature of the enzyme active site do you expect to increase the acidity of C-2? (Hint: The transfer of the double bond on to the C-2 atom is directly linked to and stabilized by the ability of the carboxyl group of 2-PG to become -2 charged.) C. Using acid-base catalysis terminology, state the roles for Glu211 and Lys345 in step 1. In other words, what do the two side chains serve as? To fulfill their roles, do you expect Glu211 and Lys345 to have modified pka's as compared to those of free Glu and Lys side chains? If so, do you expect elevated or decreased pKa's for these residues within d. the context of the active site of enolase?
Transcribed Image Text:b. The C-2 atom in 2-phosphoglycerate is not acidic in solution, i.e. it does not have a tendency to lose its proton (colored blue above). However, in the active site of enolase, C-2 has a lowered pKa and is acidic enough that Lys45 can extract its proton. Which feature of the enzyme active site do you expect to increase the acidity of C-2? (Hint: The transfer of the double bond on to the C-2 atom is directly linked to and stabilized by the ability of the carboxyl group of 2-PG to become -2 charged.) C. Using acid-base catalysis terminology, state the roles for Glu211 and Lys345 in step 1. In other words, what do the two side chains serve as? To fulfill their roles, do you expect Glu211 and Lys345 to have modified pka's as compared to those of free Glu and Lys side chains? If so, do you expect elevated or decreased pKa's for these residues within d. the context of the active site of enolase?
3. The enzyme enolase catalyzes the removal of one water molecule ("dehydration") of 2- Phosphoglycerate (2-PGA). The numbering scheme of the enolase carbons is labeled HC-0-P-O + H20 on 2-PGA. || CH2 HO-CH2 2-Phosphoglycerate Phosphoenolpyruvate Part of the catalytic mechanism is as follows: Mg2+ PO?- Mg?+ PO? 'o. Ó H Mg?+ Mg²+; PO? :-C-H C=C-C-H OH OH Нон Enolase но но H-N*-H Lys345 Lys345 Glu211 Glu211 2-Phosphoglycerate bound to enzyme Enolate intermediate Phosphoenolpyruvate а. Draw the mechanism of the reaction by adding arrows to show how electrons move. Mg2+ PO?- Mg2+ po PO H H Mg2+ С -с-с-н Mg2+ C=c-C-H H OH OH Enolase H. H-N-H но но .. H-N-H Lys345 Lys345 Glu211 Glu211 2-Phosphoglycerate bound to enzyme Enolate intermediate Mg?+ PO O. он Mg2+: PO? c=C-C-H OH HOH H но C=C H-N*-H Lys345 Glu211 Enolate intermediate Phosphoenolpyruvate
Transcribed Image Text:3. The enzyme enolase catalyzes the removal of one water molecule ("dehydration") of 2- Phosphoglycerate (2-PGA). The numbering scheme of the enolase carbons is labeled HC-0-P-O + H20 on 2-PGA. || CH2 HO-CH2 2-Phosphoglycerate Phosphoenolpyruvate Part of the catalytic mechanism is as follows: Mg2+ PO?- Mg?+ PO? 'o. Ó H Mg?+ Mg²+; PO? :-C-H C=C-C-H OH OH Нон Enolase но но H-N*-H Lys345 Lys345 Glu211 Glu211 2-Phosphoglycerate bound to enzyme Enolate intermediate Phosphoenolpyruvate а. Draw the mechanism of the reaction by adding arrows to show how electrons move. Mg2+ PO?- Mg2+ po PO H H Mg2+ С -с-с-н Mg2+ C=c-C-H H OH OH Enolase H. H-N-H но но .. H-N-H Lys345 Lys345 Glu211 Glu211 2-Phosphoglycerate bound to enzyme Enolate intermediate Mg?+ PO O. он Mg2+: PO? c=C-C-H OH HOH H но C=C H-N*-H Lys345 Glu211 Enolate intermediate Phosphoenolpyruvate
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