L25: Enzyme Kinetics 2

• Who are the authors associated with the lecture on enzyme kinetics?

  1. Robert Spooner and Dean Burk
• What is the purpose of estimating $V_{max}$ and $K_M$ in enzyme kinetics?


  To understand enzyme activity by analyzing graphical data.
• What geometric shape is formed when slicing a double cone vertically?

  A rectangular hyperbola
• What transformation did Lineweaver and Burk apply to the Michaelis-Menten equation?

  They converted it to reciprocal values to create a linear transformation.
• What does the y-axis intercept of a Lineweaver-Burk plot represent?

  It represents $1/V_{max}$.
• What does the x-axis intercept of a Lineweaver-Burk plot indicate?

  It indicates $-1/K_M$.
• What are the key features of the Lineweaver-Burk plot?

  • Y-axis intercept: $1/V_{max}$
  • X-axis intercept: $-1/K_M$
  • Gradient: $K_M/V_{max}$
  • Drawback: Excessive influence from low substrate concentrations
• Why is knowing the value of $V_{max}$ important?


  It helps determine the catalytic power or turnover number $k_{cat}$.
• How does increasing temperature affect enzyme activity?

  It increases collisions between enzyme and substrate but can also lead to reversible inactivation.
• What is the pH optimum for mammalian pepsin?

  1.5 - 2
• How does pH affect enzyme-catalyzed reactions?

  Rates vary with pH and can denature enzymes at extremes.
• How do penicillins inhibit enzyme action?

  They irreversibly inhibit penicillin-binding proteins necessary for bacterial cell wall synthesis.
• What is the mode of action of mercuric compounds in enzyme inhibition?

  They cause irreversible inactivation by covalently modifying cysteine residues.
• How does the nerve gas DIPF inactivate acetylcholinesterase?

  It reacts with a serine in the active site, leading to irreversible inhibition.
• What is Novichok and its effect on acetylcholinesterase?

  Novichok is a nerve agent that inhibits acetylcholinesterase.
• What is the effect of competitive inhibition on enzyme kinetics?

  It reduces initial reaction rates and increases $K_M$.
• What is the role of angiotensin-converting enzyme (ACE) inhibitors in medicine?

  They are used to treat hypertension and related conditions by inhibiting ACE.
• How does noncompetitive inhibition affect enzyme kinetics?

  It reduces initial reaction rates without altering $K_M$.
• How do noncompetitive inhibitors affect enzyme conformation?

  They bind at a site that is not the active site, altering the enzyme's conformation.
• What is allosteric regulation in enzymes?

  • Involves turning enzymes 'on' and 'off'
  • Alters enzyme activity through conformational changes
  • Important for regulating metabolic pathways