In-depth Notes on Enzymes and Their Mechanisms

Structural Proteins
- Provide mechanical support to cells and organisms (e.g., microtubules).
- Contribute strength to bones, skin, and tendons (e.g., collagen, keratin).
Enzymes
- Act as biological catalysts for cellular chemical reactions.
Transport and Storage Proteins
- Function as carriers for small biomolecules (e.g., hemoglobin carries oxygen).
Muscle Contraction and Mobility
- Proteins like actin and myosin are fundamental in skeletal muscle function.
Immune Proteins
- Proteins like antibodies destroy foreign substances such as viruses and bacteria.
Regulatory and Receptor Proteins
- Regulate cellular activity (e.g., hormones, DNA-binding proteins).
- Receptors mediate hormonal signals.

Central Role in Biochemical Processes:
- Essential for self-replication and catalyzing chemical reactions efficiently.
Key Characteristics:
- Primarily proteins (some RNA-based).
- Typically end with the suffix "-ase".
- Act as catalysts to increase reaction rates without being consumed.
- Exhibit high specificity, acting on specific substrates.
Enzyme Deficiency and Disease:
- Many inherited diseases result from reduced or absent enzyme activity.

Kcat (Turnover Number):
- Indicates the speed of an enzyme when bound to its substrate.
- Represents the number of substrate molecules converted to product per enzyme molecule per unit time.
- Higher $K_{cat}$ values correlate with faster reactions.

Molecular Weight: Ranges from 12,000 to over 1 million.
Holoenzyme: The active enzyme complex with its bound cofactors.
Apoenzyme: The protein component of a holoenzyme.
Cofactors: Non-protein components required for enzyme activity, such as metal ions.
Coenzymes: Organic molecules (often vitamins) that assist enzymes in catalysis.

Oxidoreductases: Catalyze oxidation-reduction reactions.
Transferases: Transfer functional groups between molecules.
Hydrolases: Catalyze hydrolysis reactions, transferring functional groups to water.
Lyases: Add or remove groups to form or break double bonds.
Isomerases: Rearrange molecular structures.
Ligases (Synthases): Join two molecules, usually using ATP energy.
Translocases: Move ions or molecules across membranes.

Enzyme-Substrate Complex:
- Forms when an enzyme binds to its substrate, leading to the transformation into products.
Transition State:
- The configuration of the substrate at its highest energy state.
Free Energy Change (ΔG):
- Formula: 1\Delta G = \Delta H - T\Delta S
- Negative $ΔG$ indicates spontaneous reactions; positive indicates non-spontaneous.

Enzymes lower the activation energy required for reactions, thus increasing reaction rates without altering $ΔG°$ .
Catalytic Strategies:
- Stabilizing the transition state to accelerate reactions.

Lock and Key Model:
- The substrate fits precisely into the enzyme’s active site.
Induced Fit Model:
- The binding of the substrate induces a conformational change in the enzyme, enhancing the fit and catalytic activity.

Composed of amino acids from different parts of the protein structure, it is crucial for the enzyme’s specificity and function.
It creates a unique microenvironment that facilitates substrate binding and catalysis.
Enzyme specificity arises from the architectural arrangement of the active site, enabling selective interactions with substrates.

Enzymes are biological catalysts essential for various biochemical reactions, with specific functions based on their structure.
The mechanism of enzyme action involves the formation of a transient enzyme-substrate complex, the stabilization of the transition state, and the lowering of activation energy to facilitate swift conversions from substrates to products.