Enzyme Targets in Medicine

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Questions and Answers

What suffix do enzymes typically have?

  • ase (correct)
  • ite
  • ine
  • in

What role do enzymes play in chemical reactions?

  • They increase the activation energy required.
  • They completely consume substrates during the reaction.
  • They act as substrates for other reactions.
  • They speed up reactions by lowering activation energy. (correct)

Which of the following is an example of an enzyme?

  • Lactic acid
  • LDH (correct)
  • NADH
  • Pyruvic acid

What is one of the primary functions of enzymes in the body?

<p>To facilitate and accelerate biochemical reactions. (B)</p> Signup and view all the answers

In the context of enzyme action, what does the term 'transition state' refer to?

<p>The point at which substrates convert to products. (D)</p> Signup and view all the answers

What type of inhibitors does Orlistat represent?

<p>Irreversible inhibitors (B)</p> Signup and view all the answers

Which enzyme does Orlistat inhibit?

<p>Pancreatic lipase (D)</p> Signup and view all the answers

What is the primary effect of Orlistat on fat absorption?

<p>Reduces fat absorption (D)</p> Signup and view all the answers

Which of the following is NOT an example of an irreversible inhibitor?

<p>Ibuprofen (D)</p> Signup and view all the answers

What is a consequence of Orlistat inhibiting pancreatic lipase?

<p>Reduced biosynthesis of fat (C)</p> Signup and view all the answers

What characterizes reversible inhibitors?

<p>They bind to the active site through intermolecular bonds. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of irreversible inhibitors?

<p>Inhibition can be overcome by increasing substrate concentration. (B)</p> Signup and view all the answers

What is a common feature of reversible inhibitors?

<p>Inhibition is dependent on inhibitor concentration. (B)</p> Signup and view all the answers

Which of the following statements is true regarding enzyme inhibitors?

<p>Reversible inhibitors do not undergo any reaction. (A)</p> Signup and view all the answers

What can increase the likelihood of inhibition by reversible inhibitors?

<p>Increasing the strength of inhibitor binding. (D)</p> Signup and view all the answers

What is the role of an allosteric inhibitor in enzyme function?

<p>It binds to the allosteric site and alters enzyme shape. (B)</p> Signup and view all the answers

How does increasing substrate concentration affect allosteric inhibition?

<p>It has no effect on the inhibition. (C)</p> Signup and view all the answers

What type of enzyme inhibitor is designed to mimic the transition state of a reaction?

<p>Transition state inhibitors (D)</p> Signup and view all the answers

What happens to the enzyme's active site when an allosteric inhibitor binds?

<p>The active site is distorted and unrecognizable. (A)</p> Signup and view all the answers

What characteristic do transition-state inhibitors share with substrates or products?

<p>They are thermodynamically stable. (D)</p> Signup and view all the answers

What bonds are formed between an allosteric inhibitor and the enzyme?

<p>Intermolecular bonds (B)</p> Signup and view all the answers

Which type of inhibitors generally bind most strongly to the active site?

<p>Transition state inhibitors (A)</p> Signup and view all the answers

What is a key difference between an allosteric inhibitor and a substrate?

<p>Allosteric inhibitors are not similar in structure to substrates. (C)</p> Signup and view all the answers

Which type of bonding force is NOT involved in substrate binding?

<p>Covalent bonds (C)</p> Signup and view all the answers

What role does ionised histidine play in acid/base catalysis?

<p>It acts as a proton source. (A)</p> Signup and view all the answers

What effect does an allosteric inhibitor have on an enzyme?

<p>It induces a conformational change that alters the active site. (D)</p> Signup and view all the answers

Which statement about enzyme regulation through feedback control is true?

<p>The final product of a pathway can inhibit the first enzyme. (C)</p> Signup and view all the answers

What do binding interactions in enzyme catalysis need to strike a balance between?

<p>Sufficient strength and sufficient weakness. (A)</p> Signup and view all the answers

What is the purpose of the allosteric site on an enzyme?

<p>To regulate enzyme activity. (B)</p> Signup and view all the answers

Which amino acid can act as a nucleophile in enzymatic reactions?

<p>L-Serine (A)</p> Signup and view all the answers

What occurs to the active site when an allosteric inhibitor binds?

<p>It undergoes shape changes making it unrecognizable. (C)</p> Signup and view all the answers

Why do stronger binding interactions in enzyme inhibitors block the active site?

<p>They prevent correct substrate alignment. (A)</p> Signup and view all the answers

In what way does an allosteric activator differ from an allosteric inhibitor?

<p>Activators enhance enzyme activity. (A)</p> Signup and view all the answers

What does the 'induced fit' model suggest about enzyme and substrate interactions?

<p>The enzyme and substrate undergo conformational changes. (D)</p> Signup and view all the answers

How does the transition state relate to substrate binding?

<p>It stabilizes substrate interaction for the reaction to occur. (A)</p> Signup and view all the answers

What type of catalysis does histidine perform when it acts as a proton sink?

<p>Base catalysis (A)</p> Signup and view all the answers

What is a characteristic of enzymatic reactions in biosynthetic pathways?

<p>The end product often regulates an early enzyme. (D)</p> Signup and view all the answers

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Study Notes

Structure and Function of Enzymes

  • Enzymes typically end with the suffix "ase".
  • Globular proteins serve as catalysts, increasing reaction speed to reach equilibrium.
  • They lower the activation energy needed for reactions.

Enzyme Interaction with Substrates

  • Substrates bind to the enzyme's active site through various interactions: hydrogen bonds, van der Waals forces, and ionic bonds.
  • Effective substrate binding relies on a balance of strong and weak interactions to stabilize the transition state.

Catalysis Mechanisms

  • Acid/base catalysis occurs with residues like histidine, which alternates between basic and acidic states.
  • Nucleophilic residues, like L-Serine and L-Cysteine, contribute to catalytic activity through their side chains.

Regulation of Enzymes

  • Allosteric inhibitors bind to sites distinct from the active site, altering the enzyme's shape and preventing substrate recognition.
  • Inhibition is not overcome by increased substrate concentration and involves structural differences between the inhibitor and substrate.

Biosynthetic Pathways and Feedback Control

  • Allosteric enzymes often regulate the beginning of biosynthetic pathways.
  • The final product of a pathway can inhibit the pathway's initial enzyme, demonstrating feedback control.

Overall Process of Enzyme Catalysis

  • The binding of substrates requires sufficient duration for the reaction, with stable interactions during transition states.
  • Strong binding interactions can lead to enzyme inhibitors that block the active site from substrates.

Types of Enzyme Inhibitors

  • Reversible inhibitors bind to the active site through weak intermolecular bonds and can be displaced by increased substrate concentration.

    • Examples include diuretics, ACE inhibitors, and statins.
  • Irreversible inhibitors form covalent bonds with enzymes, inhibiting substrate access regardless of concentration.

    • Examples include nerve gases and penicillins.

Orlistat as a Case Study

  • Orlistat inhibits pancreatic lipase, blocking fat digestion in the intestine.
  • This results in reduced absorption of fatty acids and glycerol, decreasing fat synthesis in the body.

Allosteric Inhibitors

  • Function by binding reversibly to allosteric sites, causing shape alterations in enzymes that hide the active site.
  • Inhibition remains even with high substrate concentrations, and the inhibitor differs from substrate structure.

Transition State Inhibitors

  • Designed to mimic the transition state in enzyme reactions.
  • Bind tightly to active sites and can be thermodynamically stable, offering a potential method for drug design, such as Saquinavir used in HIV treatment.

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