Enzymes Biomolecules that catalyze chemical reactions Increase reaction
Enzymes Biomolecules that catalyze chemical reactions - Increase reaction rates - Specific Oxidoreductases – catalyze redox reactions Transferases – transfer groups such as –CH 3 or -NH 2 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 Enzyme Activity - a measure of the rate of the reaction catalyzed by the enzyme Activation - an increase in enzymatic activity (how well an enzyme works) Inhibition - a decrease in enzyme activity Inhibitor - a molecule that binds to the enzyme and inhibits activity
Mechanism of Enzyme Action Lock 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 E + P
Induced Fit E+S
Induced Fit E+S
Induced Fit E + S ES
Induced Fit E + S E + P
Example: Hexokinase specifically binds both glucose and ATP Hexokinase 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 E + S ⇌ ES → E + P Temperature p. H Inhibitors
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
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