Basics of enzyme kinetics graphs
Basic enzyme kinetics graphs
Enzyme kinetics graphs and inhibitors
- Competitive inhibitors impair reaction progress by binding to an enzyme, often at the active site, and preventing the real substrate from binding. At any given time, only the competitive inhibitor or the substrate can be bound to the enzyme (not both). That is, the inhibitor and substrate compete for the enzyme. Competitive inhibition acts by decreasing the number of enzyme molecules available to bind the substrate.
- Noncompetitive inhibitors don’t prevent the substrate from binding to the enzyme. In fact, the inhibitor and substrate don't affect one another's binding to the enzyme at all. However, when the inhibitor is bound, the enzyme cannot catalyze its reaction to produce a product. Thus, noncompetitive inhibition acts by reducing the number of functional enzyme molecules that can carry out a reaction.
- With a competitive inhibitor, the reaction can eventually reach its normal , but it takes a higher concentration of substrate to get it there. In other words, is unchanged, but the apparent is higher. Why must more substrate be added in order to reach ? The extra substrate makes the substrate molecules abundant enough to consistently “beat” the inhibitor molecules to the enzyme.
- With a noncompetitive inhibitor, the reaction can never reach its normal , regardless of how much substrate we add. A subset of the enzyme molecules will always be “poisoned” by the inhibitor, so the effective concentration of enzyme (which determines ) is reduced. However, the reaction reaches half of its new at the same substrate concentration, so is unchanged. The unchanged reflects that the inhibitor doesn't affect binding of enzyme to substrate, just lowers the concentration of usable enzyme.