ENZYMES

 

ENZYMES

PREPARED BY MR. ABHIJIT DAS

DEFINITION

Enzymes are biological molecules (typically proteins) that act as catalysts, speeding up chemical reactions in living organisms. They work by lowering the activation energy required for a reaction to occur.

IUBMB CLASSIFICATION

The International Union of Biochemistry and Molecular Biology (IUBMB) classification system is based on a numerical nomenclature system called the Enzyme Commission (EC) classification. The IUBMB categorizes enzymes into six main classes:

1.     EC 1 - Oxidoreductases: Enzymes involved in oxidation-reduction reactions, facilitating the transfer of electrons from one molecule to another.

2.     EC 2 - Transferases: Enzymes that transfer functional groups (e.g., methyl, phosphate, acetyl groups) from one molecule to another.

3.     EC 3 - Hydrolases: Enzymes that catalyze hydrolytic reactions, breaking down compounds by adding water.

4.     EC 4 - Lyases: Enzymes that cleave chemical bonds without hydrolysis or oxidation.

5.     EC 5 - Isomerases: Enzymes that catalyze the rearrangement of the structure of molecules, converting one isomer into another.

6.     EC 6 - Ligases or Synthetases: These enzymes join two molecules together using the energy derived from the hydrolysis of ATP.

 

MECHANISM OF ACTION OF ENZYMES

1.     Specificity: Enzymes are highly specific, each designed for a particular reaction.

2.     Lock and Key Model: Enzymes (lock) fit with substrates (key) like a lock and key.

3.     Induced Fit: Enzymes change shape to fit the substrate, enhancing the reaction.

4.     Catalysis: Enzymes lower activation energy, accelerating reactions.

5.     Reusability: Enzymes remain unchanged and available for multiple reactions, maximizing efficiency in biological processes.

FACTORS AFFECTING ENZYME ACTIVITY

1.     Temperature: Enzymes have an optimal temperature for activity. Too high a temperature can denature them, while lower temperatures can decrease their activity.

2.     pH: Enzymes work best within specific pH ranges. Deviations from the optimal pH can alter their structure and affect their activity.

3.     Substrate Concentration: An increase in substrate concentration usually enhances the rate of reaction until the enzyme becomes saturated.

4.     Inhibitors: Substances (competitive or non-competitive inhibitors) can obstruct or reduce enzyme activity by binding to the active site or elsewhere on the enzyme.

5.     Enzyme Concentration: Generally, an increase in enzyme concentration leads to higher reaction rates, given there's an excess of substrate.

ENZYME INHIBITORS

Enzyme inhibitors are molecules that can interfere with the activity of enzymes. They can be divided into two main types: competitive and non-competitive inhibitors.

1.     COMPETITIVE INHIBITORS:

Ø  These inhibitors resemble the substrate and compete for the enzyme's active site.

Ø  When a competitive inhibitor occupies the active site, the substrate can't bind effectively, thus reducing the enzyme's activity.

Ø  Increasing substrate concentration can help overcome the effect of competitive inhibitors, as more substrate molecules increase the chances of successfully binding to the enzyme's active site despite the presence of the inhibitor.

2.     NON-COMPETITIVE INHIBITORS:

Ø  These inhibitors do not compete for the active site but instead bind to a different site on the enzyme (allosteric site).

Ø  Once attached, they cause a conformational change in the enzyme's structure, affecting the active site's functionality.

Ø  Increasing substrate concentration doesn't alleviate the impact of non-competitive inhibitors since they don't compete for the active site.

PROPERTIES OF ENZYMES

1.     Specificity: Enzymes are highly specific, designed to catalyze particular reactions or classes of reactions.

2.     Catalytic Activity: They accelerate the rate of chemical reactions by lowering the activation energy required for the reaction to occur.

3.     Reusability: Enzymes are not consumed during the reaction and remain available for multiple cycles, enhancing their efficiency.

4.     pH Sensitivity: Enzymes function optimally within specific pH ranges. Changes in pH can affect their activity.

5.     Temperature Sensitivity: Enzymes have an optimal temperature for activity, and extreme temperatures can denature them, reducing their function.

6.     Regulation by Cofactors: Some enzymes require additional non-protein molecules (cofactors or coenzymes) to function effectively.

THERAPEUTIC AND PHARMACEUTICAL IMPORTANCE OF ENZYMES

1.     Disease Diagnosis: Enzymes help identify diseases through blood tests by showing changes in enzyme levels, indicating specific health conditions.

2.     Drug Development: Understanding enzymes aids in creating new medications that either block or boost their actions, offering treatments for different illnesses.

3.     Enzyme Therapy: Enzyme replacement therapy involves giving patients the missing enzymes, treating diseases caused by enzyme deficiencies.

4.     Biological Detergents: Enzymes in detergents help remove stains by breaking down proteins and fats more efficiently than traditional detergents.

5.     Food Industry: Enzymes are used in food processing to improve quality, aid in fermentation, and enhance the production of food and beverages.