Lys345 abstracts a proton by general base catalysis. Two Mg2+ ions stabilize the resulting enolate intermediate. Glu211 facilitates elimination of the Mg2+ PO? Mg?+ PO -OH group by general acid catalysis. H он Mg²+- Mg2+: PO C-C-H OH OH НОН Enolase Но H но H-N-H H-N*-H 2 Lys345 Lys345 Glu211 Glu211 2-Phosphoglycerate bound to enzyme Enolate intermediate Phosphoenolpyruvate Figure 6-26a Lehninger Principles of Biochemistry, Sixth Edition © 2013 W. H. Freeman and Company =

Lys345 abstracts a proton by general base catalysis. Two Mg2+ ions stabilize the resulting enolate intermediate. Glu211 facilitates elimination of the Mg2+ PO? Mg?+ PO -OH group by general acid catalysis. H он Mg²+- Mg2+: PO C-C-H OH OH НОН Enolase Но H но H-N-H H-N*-H 2 Lys345 Lys345 Glu211 Glu211 2-Phosphoglycerate bound to enzyme Enolate intermediate Phosphoenolpyruvate Figure 6-26a Lehninger Principles of Biochemistry, Sixth Edition © 2013 W. H. Freeman and Company =

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter26: Synthesis And Degradation Of Nucleotides

Section: Chapter Questions

Problem 21P

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Using the ActiveModel for phosphofructokinase (Trypanosoma), describe the difference between the APO1, AP02, and holoenzyme conformations.
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Describe the experimental evidence that supports lysozyme’s catalysis by acid– base catalysis, covalent catalysis, and transition state stabilization.
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The active site of lysozyme contains two amino acid residues essential for catalysis: Glu35 and Asp52. The pKa values of the carboxyl side chains of these residues are 5.9 and 4.5, respectively. What is the ionization state(protonated or deprotonated) of each residue at pH 5.2, the pH optimum of lysozyme? How can the ionization states of these residues explain the pH-activity profile of lysozyme shown below?
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?
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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?
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