enzymes biomolecules that catalyze chemical reactions - increase reaction rates - specific...

EnzymesBiomolecules that catalyze chemical reactions

- Increase reaction rates

- Specific

Oxidoreductases – catalyze redox reactions

Transferases – transfer groups such as –CH3 or -NH2

Hydrolases – catalyze hydrolysis reactions

Lyases – catalyze the removal or addition of double bonds

Isomerases – catalyze isomerization reactions

Ligases – catalyze the joining of two molecules

Terms

Substrate - a compound that binds to the enzyme and is processed

Active Site - region (pocket or cleft) in the enzyme where the substrate binds

Activation - an increase in enzymatic activity (how well an enzyme works)

Enzyme Activity

- a measure of the rate of the reaction catalyzed by the enzyme

Inhibition - a decrease in enzyme activity

Inhibitor - a molecule that binds to the enzyme and inhibits activity

Mechanism of Enzyme ActionLock and Key

Induced Fit - substrate binding induces conformational changes

(structural changes) in the enzyme that promote catalysis

Lock and Key

E + S

Lock and Key

E + S ES

Lock and Key

E + S ES E + P

Induced Fit

E + S

Induced Fit

E + S

Induced Fit

E + S ES

Induced Fit

E + S ES E + P

Example: Hexokinase

Hexokinase specifically binds both glucose and ATPHexokinase speeds up the reaction

Glucose Binding

Glucose Binding

Hexokinase binds Glucose and ATP

Substrate binding is governed by intermolecular forces

Example of Induced Fit

Example of Induced Fit

Citrate Synthase

Krebs Cycle

Citrate Synthase

Factors that effect enzyme activity

Enzyme and Substrate Concentration

Temperature

pH

Inhibitors

E + S ES → E + P⇌

Competitive vs Noncompetitive Inhibition

Some Drugs are Enzyme Inhibitors

• Certain drugs bind to Enzymes and prevent binding of the normal substrates

• The enzyme is thus prevented from catalyzing a physiological reaction

HIV Drugs

N NH

O

NH

O

O

NH2

NH

O

NH3+

O

NH

O

O