ENZYMES

Outline for Enzymes

I. Introduction to Enzymes

  • ENZYMES

    • act as catalysts — substance that increase the rate of reaction without being consumed by the chemical reaction

  • Importance in biological processes:

    • elevated enzymes may be due to a. Pathologic or;b. Physiologic causes.

II. Types of Enzymes

  • Plasma- Specific

  • Non-plasma-specific

    • Non-plasma specific enzymes are enzymes that are not restricted to or primarily found in plasma or blood. They can be present in various tissues and perform functions unrelated to blood plasma. Examples include:

      • Lactate dehydrogenase (LDH): Found in many tissues, involved in energy production.

      • Creatine kinase (CK): Primarily in muscle and brain, involved in energy metabolism.

      These enzymes can be used as biomarkers for tissue damage or disease.

III. ENZYME KINETICS

A. Introduction to Enzymes

  • Enzymes:

    • substance that hastens biochemical reaction without being consumed

  • Role of enzymes as biological catalysts

  • Importance in metabolic processes

B. Basic Concepts

  • Active Site: Region where the substrate binds

  • Binding Site: sequences of amino acids which determines the specificity of the enzyme

  • Allosteric Site:

    • Aka the regulatory site

    • Allows molecules to either activate or inhibit the enzyme activity

    • Binds to regulatory molecule that may change in shape, resulting to the inactivation of the enzyme for its substrate

  • Substrate: Reactant that enzymes act upon

  • Product: Result of enzyme-substrate reaction

  • Enzyme Saturation: velocity plateaued even when substrate concentration increases

  • An enzyme-substrate complex is a temporary molecular structure formed when an enzyme binds to its specific substrate. This interaction occurs at the enzyme's active site, where the substrate fits like a key in a lock. The formation of this complex is crucial for catalyzing biochemical reactions, as it lowers the activation energy required for the reaction to proceed, ultimately leading to the conversion of substrates into products.

  • The Lineweaver-Burke plot is a double-reciprocal graph used in enzyme kinetics to determine the kinetic parameters of an enzyme-catalyzed reaction. It is derived from the Michaelis-Menten equation and plots ( \frac{1}{v} ) (reaction velocity) against ( \frac{1}{[S]} ) (substrate concentration). The slope of the line represents ( \frac{K_m}{V_{max}} ), the y-intercept represents ( \frac{1}{V_{max}} ), and the x-intercept represents ( -\frac{1}{K_m} ). This method helps visualize enzyme inhibition and calculate kinetic constants.

C. Enzyme Activity

  • Factors affecting enzyme activity:

    • Temperature

    • pH

    • Substrate concentration:

      • Enzyme concentration:

        Enzyme concentration INCREASE= rate of rxn. INCREASE

    • Presence of inhibitors or activators

    • Free energy (available kinetic energy)

D. Michaelis-Menten Kinetics

  • Michaelis-Menten Equation:

    • ( v = \frac{V_{max} [S]}{K_m + [S]} )

    • Where:

      • ( v ) = reaction velocity

      • ( V_{max} ) = maximum velocity

      • ( [S] ) = substrate concentration

      • ( K_m ) = Michaelis constant

  • Assumptions:

    • Steady-state assumption

    • Formation of enzyme-substrate complex

E. Key Parameters

  • Vmax: Maximum rate of reaction

  • Km: Substrate concentration at which reaction rate is half of Vmax

  • Turnover Number (kcat): Number of substrate molecules converted to product per enzyme molecule per second

F. Enzyme Inhibition

  • Types of inhibitors:

    • Competitive Inhibition: Inhibitor competes with substrate for active site

    • Non-competitive Inhibition: Inhibitor binds to enzyme or enzyme-substrate complex

    • Uncompetitive Inhibition: Inhibitor binds only to enzyme-substrate complex

  • Effects on Vmax and Km

G. Allosteric Regulation

  • Definition of allosteric enzymes

  • Mechanism of allosteric regulation

  • Sigmoidal kinetics vs. hyperbolic kinetics

H. Applications of Enzyme Kinetics

  • Drug design and pharmacology

  • Biotechnology and industrial applications

  • Clinical diagnostics

I. Conclusion

  • Summary of key points

  • Importance of understanding enzyme kinetics in biological and industrial contexts

IV. Factors Affecting Enzyme Activity

  • Temperature

    • Optimal temperature range

    • Denaturation effects

  • pH levels

    • Optimal pH for different enzymes

    • Effects of extreme pH

  • Substrate concentration

    • Michaelis-Menten kinetics

    • Saturation point

V. Enzyme Regulation

  • Types of regulation

    • Allosteric regulation

    • Covalent modification

  • Inhibition

    • Competitive inhibition

    • Non-competitive inhibition

    • Uncompetitive inhibition

VI. Enzyme Applications

  • Industrial uses

    • Food industry (e.g., amylase in brewing)

    • Biotechnology (e.g., DNA polymerase in PCR)

  • Medical applications

    • Diagnostic enzymes (e.g., glucose oxidase)

    • Therapeutic enzymes (e.g., enzyme replacement therapy)

VII. Conclusion

  • Summary of key points

  • Future directions in enzyme research

  • Importance of enzymes in health and industry