ENZYMES 

Mind ma 

ENZYMES — SHORT NOTE (Exam Oriented)

Reference: Satyanarayan

Definition-Enzymes are biological catalysts, mostly proteins, that speed up biochemical reactions without being consumed.

Key Characteristics

Highly specific for substrates

Lower activation energy

Remain unchanged after reaction

Active at optimum pH & temperature

Mostly globu

Some require cofactors

Classification of Enzymes (IUBMB)

Oxidoreductases – Redox reactions

Transferases – Transfer functional groups

Hydrolases – Hydrolysis reactions

Lyases – Add/remove groups without water

Isomerases – Rearrangement reactions

Ligases – Joining molecules using ATP

Mnemonic -OTHLIL

Mechanism of Action

1)Lock and Key Model

2)Induced Fit Model

(Substrate binds to active site → product formed)

Factors Affecting Enzyme Activity

1)Temperature- optimum temprature enzyme activity is high 

At low temperature enzyme activity is stop 

At high temperature enzyme activity denaturation 

2) ph-optimum ph it will be high enzyme activity 

3)Substrate concentration-Vmax is low high is the velocity of an enzyme and vise Versa 

4)Enzyme concentration-high concentration of enzyme High its velocity 

Enzyme Inhibition

1)Competitive – Competes with substrate

2)Non-competitive – Binds elsewhere

3)Irreversible – Permanently inactivates enzyme

Isoenzymes 

Definition:

Isoenzymes are different molecular forms of the same enzyme that catalyze the same biochemical reaction but differ in physical, chemical, kinetic properties and tissue distribution.

Characteristics

1)Same substrate specificity

2)Different amino acid composition

3)Different electrophoretic mobility

4)Different optimum pH & Km

5)Tissue specific distribution

Example

1)Lactate Dehydrogenase (LDH)

Tetrameric enzyme made of H & M subunits

5 isoenzymes:

LDH₁ (H₄) – Heart

LDH₂ (H₃M₁) – RBC

LDH₃ (H₂M₂) – Lung

LDH₄ (H₁M₃) – Kidney

LDH₅ (M₄) – Liver & Skeletal muscle

2)Creatine Kinase (CK) – Applications

Creatine kinase catalyzes the reversible transfer of phosphate between creatine and ATP. It exists as isoenzymes, useful in clinical diagnosis.

CK Isoenzymes

CK-BB (CK₁) – Brain, smooth muscle

CK-MB (CK₂) – Cardiac muscle

CK-MM (CK₃) – Skeletal muscle

Clinical Importance

Diagnostic markers (AST, ALT, ALP)

Used in therapy & biotechnology

Metabolic disease detection