,ENZYMES
1. Introduction to Enzymes
Enzymes are biological molecules that act as catalysts. A catalyst is a substance that speeds up a
chemical reaction without being permanently changed or consumed during the reaction. In living
organisms, almost all biochemical reactions digestion, respiration, DNA replication, muscle contraction
are controlled by enzymes.
Most enzymes are proteins composed of amino acids folded into a specific three-dimensional shape.
This shape is very important because enzyme activity depends on it. If the shape is disturbed, the
enzyme may stop working.
Key characteristics of enzymes:
• Highly specific for their substrate
• Work under mild biological conditions
• Increase reaction speed by lowering activation energy
• Not used up during reactions
• Regulated according to body needs
An enzyme binds to a substrate to form an enzyme–substrate complex, converts it into product, and
then releases the product.
Classification of Enzymes
Enzymes are grouped based on the type of reaction they catalyze. According to international
classification, there are six major classes:
Oxidoreductases
These enzymes catalyze oxidation–reduction reactions involving transfer of electrons or hydrogen
atoms.
Functions:
• Cellular respiration
• Energy production
• Detoxification
Examples:
• Dehydrogenases
• Oxidases
, Transferases
Transferases move functional groups (methyl, phosphate, amino) from one molecule to another.
Functions:
• Metabolism regulation
• Signal transmission
Examples:
• Kinases (transfer phosphate groups)
• Transaminases
Hydrolases
Hydrolases break chemical bonds using water (hydrolysis reactions).
Functions:
• Digestion of food molecules
• Cellular breakdown processes
Examples:
• Proteases
• Lipases
• Amylases
Lyases
Lyases remove groups or add groups to molecules without using ATP or water. They often form double
bonds.
Functions:
• Metabolic pathway reactions
Examples:
• Decarboxylases
• Dehydratases
Isomerases
Isomerases rearrange atoms within a molecule to form isomers.
Functions:
• Important in carbohydrate metabolism
1. Introduction to Enzymes
Enzymes are biological molecules that act as catalysts. A catalyst is a substance that speeds up a
chemical reaction without being permanently changed or consumed during the reaction. In living
organisms, almost all biochemical reactions digestion, respiration, DNA replication, muscle contraction
are controlled by enzymes.
Most enzymes are proteins composed of amino acids folded into a specific three-dimensional shape.
This shape is very important because enzyme activity depends on it. If the shape is disturbed, the
enzyme may stop working.
Key characteristics of enzymes:
• Highly specific for their substrate
• Work under mild biological conditions
• Increase reaction speed by lowering activation energy
• Not used up during reactions
• Regulated according to body needs
An enzyme binds to a substrate to form an enzyme–substrate complex, converts it into product, and
then releases the product.
Classification of Enzymes
Enzymes are grouped based on the type of reaction they catalyze. According to international
classification, there are six major classes:
Oxidoreductases
These enzymes catalyze oxidation–reduction reactions involving transfer of electrons or hydrogen
atoms.
Functions:
• Cellular respiration
• Energy production
• Detoxification
Examples:
• Dehydrogenases
• Oxidases
, Transferases
Transferases move functional groups (methyl, phosphate, amino) from one molecule to another.
Functions:
• Metabolism regulation
• Signal transmission
Examples:
• Kinases (transfer phosphate groups)
• Transaminases
Hydrolases
Hydrolases break chemical bonds using water (hydrolysis reactions).
Functions:
• Digestion of food molecules
• Cellular breakdown processes
Examples:
• Proteases
• Lipases
• Amylases
Lyases
Lyases remove groups or add groups to molecules without using ATP or water. They often form double
bonds.
Functions:
• Metabolic pathway reactions
Examples:
• Decarboxylases
• Dehydratases
Isomerases
Isomerases rearrange atoms within a molecule to form isomers.
Functions:
• Important in carbohydrate metabolism
