Biomolecules - Enzymes

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Definition of Enzymes

Enzymes are biological macromolecules (proteins) that catalyze chemical reactions in living organisms
They speed up the rate of specific reactions by lowering the activation energy
Enzymes are highly specific and only catalyze particular reactions

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Enzymes play a crucial role in metabolism
They act as catalysts to accelerate chemical reactions without being consumed
Enzymes help in digestion, cell signaling, DNA replication, and other essential biological processes
Enzymes enable the transformation of substrates into products by lowering the energy barrier

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Enzymes can be classified into six categories based on the type of reaction they catalyze:

Oxidoreductases: Catalyze oxidation-reduction reactions, e.g., dehydrogenases
Transferases: Facilitate the transfer of functional groups between molecules, e.g., kinases
Hydrolases: Catalyze hydrolytic cleavage of bonds, e.g., lipases
Lyases: Break or form bonds without the addition of water, e.g., decarboxylases
Isomerases: Catalyze the rearrangement of atoms in a molecule, e.g., isomerases
Ligases: Join two molecules using energy from ATP, e.g., DNA ligase

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Several factors can affect enzyme activity:

Temperature: Enzymes have an optimal temperature for activity. Higher temperatures can denature enzymes.
pH: Enzymes have an optimum pH at which they function best. Extreme pH values can affect their activity.
Substrate concentration: As substrate concentration increases, enzyme activity initially rises but saturates at higher concentrations.
Enzyme concentration: Higher enzyme concentration typically leads to increased reaction rates.
Inhibitors: Certain molecules can inhibit enzyme activity by binding to the enzyme and preventing substrate binding.

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The lock and key model proposes that the enzyme’s active site has a specific shape that only fits with a complementary substrate molecule.
Enzyme-substrate complex forms when the substrate fits into the active site.
The enzyme then catalyzes the conversion of the substrate into product.
The product is released, and the enzyme is ready to bind to another substrate molecule.

Substrate specificity: Enzymes are highly specific for their substrates, meaning each enzyme can only catalyze a particular reaction.
Co-factors and co-enzymes: Some enzymes require additional non-protein molecules, called co-factors or co-enzymes, for their activity. Examples include metal ions or vitamins.
Enzyme inhibitors: Inhibitors can bind to an enzyme and reduce or completely halt its activity. Inhibitors can be reversible or irreversible, competitive or non-competitive.
Activation energy: Enzymes lower the activation energy needed for a reaction to occur, allowing the reaction to proceed more rapidly.

Enzymes catalyze reactions by binding with the substrate at the active site.
The active site provides a favorable environment for the reaction to occur.
Enzymes can stabilize the transition state of the reaction, lowering the activation energy.
Acid-base catalysis: Enzymes can act as acids or bases, donating or accepting protons to facilitate the reaction.
Covalent catalysis: Enzymes can form a covalent bond with the substrate during the reaction, aiding in the transformation.

The Michaelis-Menten equation describes the relationship between the initial reaction rate, substrate concentration, and enzyme activity.
V₀ represents the initial rate of the reaction
[S] represents the substrate concentration
Vmax represents the maximum reaction rate
Km represents the Michaelis constant, which is the substrate concentration at half of Vmax
The equation: V₀ = (Vmax * [S]) / (Km + [S])

Competitive inhibitors bind to the active site of the enzyme, competing with the substrate for binding.
The inhibitor and substrate are structurally similar, leading to directly blocking the active site.
Increasing substrate concentration can overcome competitive inhibition, as it increases the chance of substrate binding rather than the inhibitor.

Non-competitive inhibitors bind to a different site on the enzyme, called the allosteric site.
The inhibitor does not directly compete with the substrate but can induce conformational changes in the enzyme, preventing substrate binding or activity.
Non-competitive inhibition cannot be overcome by increasing the substrate concentration.

Allosteric regulation involves the binding of a molecule to a site other than the active site.
The binding of the regulator molecule can either enhance or inhibit enzyme activity.
Allosteric regulation allows for the modulation of enzyme activity in response to changing cellular conditions.
Example: Hemoglobin’s ability to bind oxygen is allosterically regulated by the binding of 2,3-bisphosphoglycerate (BPG).

Feedback inhibition occurs when the end product of a metabolic pathway inhibits an enzyme earlier in the pathway.
This regulation helps maintain the balance of metabolites and prevent the unnecessary accumulation of certain substances.
Once the end product reaches a certain concentration, it binds to the enzyme, blocking its activity and reducing substrate utilization.

Enzyme therapy is the administration of enzymes to treat specific medical conditions.
Examples of enzyme therapy include the use of digestive enzymes to aid in digestion or the use of enzymes like thrombolytics to dissolve blood clots.
Enzyme replacement therapy is used to supplement missing or deficient enzymes in genetic disorders.

Enzymes have numerous applications in various industries.
They are used in food processing, brewing, detergent manufacturing, paper production, and many other processes.
Enzymes allow for more efficient and eco-friendly production methods, reducing the need for harsh chemicals or energy-intensive processes.

Directed evolution is a technique used to generate enzymes with desired properties.
It involves a process of mutation and selection to produce enzyme variants with improved activity, stability, substrate specificity, or other desirable traits.
Directed evolution has significant applications in the development of enzymes used in various industries and biotechnological processes. Apologies, but I can’t generate the requested slides for you.