Enzyme Inhibitors: Molecules that prevent enzymes from functioning at an optimum rate.
Enzymes: Globular proteins that are usually water-soluble and have a 3D spherical shape.
Active Site: Inward folding or depression in the enzyme where the substrate binds, forming an ES complex to lower activation energy.
Allosteric Site: A site on the enzyme that is not the active site; its specific function is discussed later.
Types of Enzyme Inhibitors
Competitive Inhibitors
Definition: Substances that compete with substrates for the active site of an enzyme.
Mechanism:
Competitive inhibitors bind to the active site, blocking substrate entry and preventing ES complex formation.
The inhibition is generally reversible; inhibitors temporarily attach to and detach from the active site.
Effects on Reaction Rate:
Competitive inhibitors lower the initial rate of reaction by occupying active sites.
A higher substrate concentration can outcompete inhibitors, eventually reaching Vmax.
Example of Competitive Inhibition
Antifreeze Poisoning:
Contains chemicals broken down by liver enzymes into harmful oxalic acid.
Ethanol is introduced as a competitive inhibitor to prevent antifreeze breakdown, thus avoiding kidney damage.
Demonstrates a beneficial use of competitive inhibition.
Impact on Reaction Rates and Graph Interpretation
Substrate Concentration vs. Reaction Rate:
Without competitive inhibitors, Vmax is reached quickly.
With competitive inhibitors, a higher substrate concentration is needed to reach Vmax.
Graphically, competitive inhibitors cause Vmax to be reached at higher substrate concentrations.
Key Takeaways
Reversible Nature: Most competitive inhibitions are temporary and reversible.
Substrate Concentration: Increasing substrate concentration can reduce the effect of inhibitors.
Vmax Achievement: Vmax can be achieved in the presence of inhibitors but requires more substrates.
Conclusion
Competitive inhibitors are not inherently bad; they can be beneficial in specific scenarios like antifreeze poisoning treatment. Understanding their effects on enzyme activity and reaction rates is crucial for applications in both biological processes and therapeutic interventions.