Enzyme Activity and Function

Introduction to Enzymes

• Enzymes are often described as speeding up reactions, but their true function is to

  • Make and break chemical bonds.

  • Interact with substrates to convert them into products.

Structure and Function of Enzymes

• Enzymes are proteins composed of amino acids.

• The interaction between enzymes and substrates is based on molecular attraction, specifically charge compatibility.

• Example of charge correlation:

  • Enzyme: Negative, Positive, Negative, Positive

  • Substrate: Positive, Positive, Negative, Negative

• Importance of charge alignment for the effective binding of substrates to enzymes.

Effects of Mutation on Enzyme Function

• Enzymes are proteins with diverse structures:

  • Primary Structure: Nucleotide sequence

  • Secondary Structure: Amino acid sequences

  • Tertiary Structure: Overall protein structure

• Mutations can alter enzyme efficiency by changing amino acids and their charge characteristics.

• Changes in structure directly affect enzyme function – "Change the structure, change the function."

Measuring Enzyme Activity

• Efficiency measured as the percentage of substrate converted into product.

• As structural changes occur at the active site, enzyme efficiency and activity decrease.

Energy Investment in Reactions

• Enzymes reduce the energy required for reactions to occur.

• Without enzymes, reactions require greater energy input to convert substrate into product.

Enzyme-Substrate Interaction Models

• Lock and Key Model: The enzyme's active site is a rigid shape that fits perfectly with the substrate.

• Induced Fit Model: The enzyme changes shape slightly upon substrate binding, allowing for a better fit.

  • Analogy: Fitting a foot into a shoe; both adapt slightly for a snug fit.

Factors Influencing Enzyme Efficiency

• Temperature and pH:

  • Each enzyme has an optimal temperature and pH range for maximum efficiency.

  • Extreme changes can lead to denaturation, breaking ionic bonds within enzymes, rendering them nonfunctional.

  • Example of growth curves reflecting enzyme activity correlation with temperature and pH.

• Substrate Concentration:

  • Enzyme activity is affected by the amount of substrate available.

  • When enzyme active sites are fully occupied (saturation), any additional substrate has no effect on productivity.

• Chemical Inhibition:

  • Competitive Inhibitors: Bind to the active site, preventing substrate from binding. Examples include certain antibiotics.

  • Non-competitive Inhibitors: Bind to a different part of the enzyme and change its shape, reducing its functionality without occupying the active site.

Types of Inhibitors

• Reversible Competitive Inhibitors: Temporarily bind and reduce activity.

• Irreversible Competitive Inhibitors: Permanently bind, requiring cells to produce new enzymes to compensate, significantly affecting cell function.

Enzyme Regulation

• Cells naturally regulate enzyme activity using inhibition methods, which can be either competitive or noncompetitive.

• Importance of understanding enzyme mechanisms for applications in genetic regulation and therapeutic practices.

Conclusion

• Both environmental conditions and cellular mechanisms play crucial roles in enzyme activity, influencing all biological processes.