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Questions and Answers
What are enzymes?
What are enzymes?
Where is the active site located?
Where is the active site located?
What is the function of the active site?
What is the function of the active site?
What is a substrate?
What is a substrate?
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How are enzymes usually structured?
How are enzymes usually structured?
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What can be deduced about the mechanism of an enzyme?
What can be deduced about the mechanism of an enzyme?
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What is the role of enzymes in biochemical reactions?
What is the role of enzymes in biochemical reactions?
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What is the active site often formed by?
What is the active site often formed by?
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What fraction of biochemical reactions use multiple substrates?
What fraction of biochemical reactions use multiple substrates?
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What do enzymes bind to at the active site?
What do enzymes bind to at the active site?
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What is the primary role of a substrate in an enzymatically catalyzed reaction?
What is the primary role of a substrate in an enzymatically catalyzed reaction?
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What is the typical structure of the active site?
What is the typical structure of the active site?
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What is the main function of enzymes in relation to reaction rates?
What is the main function of enzymes in relation to reaction rates?
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Which enzyme classification includes enzymes that catalyze the transfer of functional groups?
Which enzyme classification includes enzymes that catalyze the transfer of functional groups?
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What does the Michaelis constant (KM) represent in the Michaelis-Menten equation?
What does the Michaelis constant (KM) represent in the Michaelis-Menten equation?
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What does the Lineweaver-Burke plot provide a graphical representation of?
What does the Lineweaver-Burke plot provide a graphical representation of?
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What does the turnover number (kcat) measure?
What does the turnover number (kcat) measure?
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At what point does the diffusion-controlled limit occur?
At what point does the diffusion-controlled limit occur?
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What characterizes irreversible inhibitors?
What characterizes irreversible inhibitors?
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In competitive inhibition, what do inhibitors compete directly with?
In competitive inhibition, what do inhibitors compete directly with?
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What is the impact of uncompetitive inhibition on Vmax and KM?
What is the impact of uncompetitive inhibition on Vmax and KM?
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What characterizes suicide inhibitors?
What characterizes suicide inhibitors?
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What is the defining feature of mixed inhibition?
What is the defining feature of mixed inhibition?
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Which enzyme classification includes enzymes that catalyze the breaking of chemical bonds through elimination reactions?
Which enzyme classification includes enzymes that catalyze the breaking of chemical bonds through elimination reactions?
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Which type of catalysis involves amino acid side chains donating or accepting protons?
Which type of catalysis involves amino acid side chains donating or accepting protons?
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What type of catalysis involves active site metal acting as a redox active center?
What type of catalysis involves active site metal acting as a redox active center?
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Which catalysis involves nucleophilic or electrophilic attack on an atom resulting in a covalent intermediate?
Which catalysis involves nucleophilic or electrophilic attack on an atom resulting in a covalent intermediate?
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What type of catalysis is sometimes referred to as electrostatic catalysis?
What type of catalysis is sometimes referred to as electrostatic catalysis?
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Which type of catalysis involves weak forces lowering entropy?
Which type of catalysis involves weak forces lowering entropy?
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In induced fit, enzymes bind substrates that favor which state?
In induced fit, enzymes bind substrates that favor which state?
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Which enzyme catalyzes the breaking of chemical bonds through elimination reactions?
Which enzyme catalyzes the breaking of chemical bonds through elimination reactions?
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What is the primary function of lysozyme?
What is the primary function of lysozyme?
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Which amino acids are involved in covalent catalysis?
Which amino acids are involved in covalent catalysis?
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What is the role of metal ions in metal ion catalysis?
What is the role of metal ions in metal ion catalysis?
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What is the impact of induced fit on the entropy of the system?
What is the impact of induced fit on the entropy of the system?
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What is the mechanism of action of lysozyme?
What is the mechanism of action of lysozyme?
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Which enzyme catalyzes the conversion of carbon dioxide to carbonic acid using Zn2+ in the active site?
Which enzyme catalyzes the conversion of carbon dioxide to carbonic acid using Zn2+ in the active site?
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Which class of proteases does chymotrypsin belong to?
Which class of proteases does chymotrypsin belong to?
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Which technique is used to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone?
Which technique is used to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone?
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Which enzyme regulation method involves altering gene expression, sequestration in compartments, limiting substrate access, and covalent modification?
Which enzyme regulation method involves altering gene expression, sequestration in compartments, limiting substrate access, and covalent modification?
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What is the inactive form of chymotrypsin?
What is the inactive form of chymotrypsin?
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Which process involves protein kinases adding phosphate groups and phosphatases removing them?
Which process involves protein kinases adding phosphate groups and phosphatases removing them?
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What type of regulation can increase or decrease enzymatic activity by binding at a site other than the active site?
What type of regulation can increase or decrease enzymatic activity by binding at a site other than the active site?
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Which enzyme is an example of regulation via phosphorylation?
Which enzyme is an example of regulation via phosphorylation?
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What is the technique to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone?
What is the technique to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone?
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What is the enzyme that degrades proteins and includes trypsin, chymotrypsin, and elastase?
What is the enzyme that degrades proteins and includes trypsin, chymotrypsin, and elastase?
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Study Notes
Enzyme Kinetics and Inhibition
- Enzyme classifications include oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
- Enzymes lower activation energy (Ea) to increase reaction rate without changing thermodynamic parameters.
- The Michaelis-Menten equation relates substrate concentration to Vmax and KM, with Vmax representing maximal velocity and KM the Michaelis constant.
- Saturation kinetic curve shows enzyme saturation with substrate and the impact of high or low KM values.
- Lineweaver-Burke plot provides a double reciprocal of the Michaelis-Menten equation, offering an easier method for interpreting graphical data.
- Turnover number (kcat) measures the number of reactions an enzyme can catalyze per unit of time, indicating catalytic efficiency.
- Diffusion controlled limit occurs when the rate-limiting step becomes the diffusion of enzyme and substrate, with a rate between 108 and 109 M−1 sec−1.
- Inhibitors can be irreversible or reversible, preventing the generation of products.
- Suicide inhibitors irreversibly block enzyme function by covalently modifying the active site, examples include pesticides and nerve agents.
- Competitive inhibition involves molecules similar to the substrate shape, competing directly with the substrate and can be overcome with high substrate concentration.
- Uncompetitive inhibition binds to the ES complex, decreasing both Vmax and KM.
- Mixed inhibition combines features of competitive and uncompetitive inhibitors, being effective regardless of substrate concentration.
Enzyme Catalysis and Regulation
- Carbonic anhydrase is found in erythrocytes and catalyzes the conversion of carbon dioxide to carbonic acid using Zn2+ in the active site.
- Proteases are enzymes that degrade proteins and include trypsin, chymotrypsin, and elastase, and are important in protein maturation, blood clotting, and protein trafficking.
- Different classes of proteases, including serine, aspartyl, metallo-, and cysteine proteases, employ similar chemistry with conserved topology and overall structure.
- Chymotrypsin is a serine protease that cleaves dietary protein and contains a catalytic triad with Aspartate, Histidine, and Serine.
- Affinity labeling is a technique to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone.
- Enzyme regulation can be achieved through altering gene expression, sequestration in compartments, limiting substrate access, and covalent modification and allosteric regulation methods.
- Covalent modification involves the covalent addition or removal of groups from proteins, with proteolytic cleavage and phosphorylation as common means of activation.
- Zymogens are inactive enzyme precursors that require proteolytic activation, with chymotrypsinogen being the inactive form of chymotrypsin.
- Phosphorylation is another example of protein activation facilitated by protein kinases adding phosphate groups and phosphatases removing them, regulated through signaling cascades.
- Src is an example of regulation via phosphorylation.
- Allosteric regulation can increase or decrease enzymatic activity by binding at a site other than the active site, with relaxed (R) and tense (T) states and sigmoidal activity curves.
- Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein. Copyright © 2019 John Wiley & Sons, Inc.
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Description
Test your knowledge of enzyme kinetics and inhibition with this quiz. Explore topics such as Michaelis-Menten equation, turnover number, saturation kinetic curve, Lineweaver-Burke plot, and various types of enzyme inhibitors including competitive, uncompetitive, and mixed inhibition.
