Which of the following statements regarding allosteric kinetics is false?

• A. The rate of an allosteric enzyme reaction is dependent on substrate concentration [S].
• B. The reaction velocity and substrate concentration always proportionally change in a Lineweaver-Burk plot.
• C. At saturating [S], the kinetics of an allosteric enzyme will follow the Michaelis-Menten model.
• D. Allosteric enzymes display second order kinetics leading to sigmoidal curvature on a kinetics plot.
• E. None are false because all of the above are true.

Answer: (B)

Verified step by step guidance

1. Understand the concept of allosteric enzymes: Allosteric enzymes are those whose activity is modulated by the binding of an effector molecule at a site other than the enzyme's active site. This can result in changes to the enzyme's activity and kinetics.
2. Review the Lineweaver-Burk plot: This is a double reciprocal plot used to illustrate the kinetics of enzyme-catalyzed reactions. For Michaelis-Menten kinetics, this plot is linear, but allosteric enzymes often do not follow this linear relationship due to their cooperative binding.
3. Examine the statement about reaction velocity and substrate concentration: In allosteric enzymes, the relationship between reaction velocity and substrate concentration is not always proportional, especially in a Lineweaver-Burk plot, due to the sigmoidal nature of their kinetics.
4. Consider the statement about Michaelis-Menten kinetics at saturating [S]: At high substrate concentrations, some allosteric enzymes can exhibit Michaelis-Menten-like kinetics, where the reaction rate becomes independent of substrate concentration.
5. Evaluate the statement about second order kinetics and sigmoidal curvature: Allosteric enzymes often display sigmoidal kinetics due to cooperative binding, which is a hallmark of second order kinetics, leading to a characteristic S-shaped curve on a kinetics plot.