7: Enzyme Kinetics
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- 7.1: Enzyme Kinetics
- Unlike uncatalyzed (but readily occurring) reactions, in which the rate of the reaction is dependent only on the concentration of the reactants, the rate of enzyme-catalyzed reactions is limited by the number of enzyme molecules available. This maximal rate of turnover from substrate to product is a function of the speed of the enzyme and the number of enzyme molecules.
- 7.2: Enzyme Activity
- Enzymes convert reactants into products by binding substrates and modifying reaction pathways to increase efficiency. Kinetics, inhibition, and regulatory mechanisms determine reaction rates. Cofactors and ribozymes contribute to enzymatic activity, while inhibitors like methotrexate prevent function by blocking substrate binding.
- 7.3: Basic Principles of Catalysis
- Thanks to catalysis, reactions that can take hundreds of years to complete in the uncatalyzed “real world,” occur in seconds in the presence of a catalyst. To understand enzymatic catalysis, it is necessary first to understand energy. Chemical reactions follow the universal trend of moving towards lower energy, but they often have a barrier in place that must be overcome. The secret to catalytic action is reducing the magnitude of that barrier.
- 7.4: Derivation of Michaelis-Menten equation
- The Michaelis-Menten equation describes how reaction rates depend on substrate concentration. Maximum velocity (Vmax) and the Michaelis constant (Km) determine catalytic efficiency and substrate affinity. Reversible inhibitors alter enzyme function, with competitive inhibitors increasing apparent Km without affecting Vmax, while noncompetitive inhibitors reduce Vmax but leave Km unchanged.
- 7.5: Binding - The First Step Towards Protein Function
- Ligand binding enables protein function through reversible noncovalent interactions. Dissociation constants (KD) and binding affinities determine macromolecule-ligand interactions. Saturation curves, graphical analysis, and binding site dynamics illustrate ligand specificity. Protein dimerization and cooperative binding influence biochemical regulation.