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5. Describe the role of His in the catalytic mechanism shown.

5. Describe the role of His in the catalytic mechanism shown.

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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### Image Transcription and Explanation for Educators #### Description of Catalytic Mechanism In the diagram shown, we have a chemical mechanism involving the amino acid Histidine (His) as part of an enzyme-driven reaction. The His residue is depicted interacting with a reaction substrate bound to coenzyme A, specifically with a thiol group (−SCoA). #### Role of His in the Catalytic Mechanism 1. **Structure Explanation:** - The structure features a substrate bound to a protein backbone with an NH3^+ group at one end. - A Histidine residue is prominently shown with its imidazole side chain, which is crucial in catalysis. 2. **Mechanism Steps:** - The His residue's nitrogen gets involved in proton exchange, aiding the thiol group (H−SCoA) interaction. - Electron movement is indicated by arrows showing a possible deprotonation or nucleophilic attack facilitated by His. - The labeled point 3 highlights the end product, likely showing how His assists in converting the initial substrate into the final product: Acetyl-CoA (CH3COSCoA). 3. **General Function:** - The catalytic mechanism suggests that His plays a vital role in stabilizing transition states and facilitating proton transfer essential for the enzymatic conversion process. Teachers can utilize this explanation to elaborate on enzyme catalysis, emphasizing Histidine's role in biological reactions and the importance of enzyme-substrate interactions.
Transcribed Image Text:### Image Transcription and Explanation for Educators #### Description of Catalytic Mechanism In the diagram shown, we have a chemical mechanism involving the amino acid Histidine (His) as part of an enzyme-driven reaction. The His residue is depicted interacting with a reaction substrate bound to coenzyme A, specifically with a thiol group (−SCoA). #### Role of His in the Catalytic Mechanism 1. **Structure Explanation:** - The structure features a substrate bound to a protein backbone with an NH3^+ group at one end. - A Histidine residue is prominently shown with its imidazole side chain, which is crucial in catalysis. 2. **Mechanism Steps:** - The His residue's nitrogen gets involved in proton exchange, aiding the thiol group (H−SCoA) interaction. - Electron movement is indicated by arrows showing a possible deprotonation or nucleophilic attack facilitated by His. - The labeled point 3 highlights the end product, likely showing how His assists in converting the initial substrate into the final product: Acetyl-CoA (CH3COSCoA). 3. **General Function:** - The catalytic mechanism suggests that His plays a vital role in stabilizing transition states and facilitating proton transfer essential for the enzymatic conversion process. Teachers can utilize this explanation to elaborate on enzyme catalysis, emphasizing Histidine's role in biological reactions and the importance of enzyme-substrate interactions.
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