Enzyme Review Enzymes are…. Enzymes work by…. Environmental factors that effect enzyme activity are….

Enzymes are… Proteins Catalysts for biological reactions something that speeds up a reaction. Up to 1012 fold Usually end in ‘…ase’. Name Identifies a reacting substance sucrase – reacts sucrose lipase - reacts lipid Name describes function of enzyme oxidase – catalyzes oxidation hydrolase – catalyzes hydrolysis

Enzymes work by… Lowering the activation energy of a reaction. Increasing the rate of reaction.

Mechanism for enzyme action: Lock and Key Model A substrate(s) fits into a binding site on the enzyme called the active site. The enzyme lowers the energy required to reach the transition state. The product(s) is/are produced.

Enzyme Action: Induced Fit Model Enzyme structure flexible, not rigid Enzyme and active site adjust shape to bind substrate Increases range of substrate specificity Shape changes also improve catalysis during reaction

Enzyme Action: Induced Fit Model E + S ES complex E + P P S S S P

Factors Affecting Enzyme Action Optimum temperature Reaction Rate Low High Temperature All enzymes have a temperature range within which they are most effective. Denaturation

Factors Affecting Enzyme Action Reaction Rate Optimum pH 3 5 7 9 11 pH

Enzyme Activity & pH: Digestive enzymes

Factors Affecting Enzyme Action Maximum activity Reaction Rate substrate concentration Enzyme cofactors Vitamins Phosphorylation May affect concen-tration and enzyme action.

Enzyme Inhibition Inhibitors -Cause a loss of catalytic activity -Change the protein structure of an enzyme -May be competitive or noncompetitive -Some effects are irreversible

Competitive Inhibition A competitive inhibitor Has a structure similar to substrate Occupies active site Competes with substrate for active site Has effect reversed by increasing substrate concentration Helps regulate the amount of product

Competitive Inhibition

Penicillin Mode of Action - Enzyme Inhibition: All penicillin derivatives work by inhibiting proper bacterial cell wall synthesis. If cell walls are improperly made cell walls allow water to flow into the cell causing it to burst.

Noncompetitive Inhibition A noncompetitive inhibitor Does not have a structure like substrate Binds to the enzyme but not active site; called the allosteric site (allo = other, steric = space) Changes the shape of enzyme and active site Substrate cannot fit altered active site No reaction occurs Effect is not reversed by adding substrate

Competitive vs. Noncompetitive Inhibition

Enzyme Inhibition May be irreversible: inhibitor permanently inactivates or destroys the enzyme. EX: poisons Cyanide is an inhibitor for the essential enzyme cytochrome c oxidase Penicillin is poison to bacteria Nerve gas inhibits acetylcholinesterase (necessary for proper nerve/muscle function).

And now a few thoughts about lab… Liver = source of enzyme catalase Hydrogen peroxide = substrate Three different variables: concentration temperature pH

Catalase Protects Cells by Destroying Hydrogen Peroxide 2H2O2 2H2O + O2 H2O2 is produced in the breakdown of fats and amino acids. H2O2 is extraordinarily reactive and will damage the cell. This occurs in an organelle called the peroxisome, which is also where catalase is found. Catalase reduces the activation energy for the reduction of H202 86-fold H2O2 is extraordinarily reactive and will damage the cell.