An Introduction to
Enzymes
Most
Enzymes Are Proteins
Enzymes Are
Classified by the Reactions They Catalyze
How Enzymes Work
Enzymes
Affect Reaction Rates, Not Equilibria
Reaction
Rates and Equilibria Have Precise Thermodynamic
Definitions
A Few
Principles Explain the Catalytic Power and
Specificity of Enzymes
Weak
Interactions between Enzyme and Substrate Are
Optimized in the Transition State
Enzymes
Use Binding Energy to Provide Reaction
Specificity and Catalysis
Specific
Catalytic Groups Contribute to Catalysis
Coualent
Catalysis
Enzyme Kinetics as
an Approach to Understanding Mechanism
Substrate
Concentration Affects the Rate of
Enzyme-Catalyzed Reactions
The
Relationship between Substrate Concentration and
Enzymatic Reaction Rate Can Be Expressed
Quantitatively
BOX 8-1
Transformations of the Michaelis-Menten Equation: The
Douhle-Reciprocal Plot
The
Meaning of Vmax and Km Is Unique for Each Enzyme
Many
Enzymes Catalyze Reactions Involving Two or More
Substrates
Pre-Steady
State Kinetics Can Provide Evidence for Specific
Reaction Steps
Enzymes
Are Subject to Reversible and Irreversible
Inhibition
BOX 8-2 Kinetic
Tests for Determining Inhibition Mechanisms
Enzyme
Activity Is Affected by pH
Examples of
Enzymatic Reactions
Reaction
Mechanisms Illustrate Principles
BOX 8-3 Evidence for
Enzyme-Transition State Complementarity
Structure-Activity
Correlations
Transition-State
Analogs
Catalytic
Antibodies
Regulatory Enzymes
Allosteric
Enzymes Are Regulated by Noncovalent Binding of
Modulators
Allosteric
Enzymes Are Exceptions to Many General Rules
Two Models
Explain the Kinetic Behavior of Allosteric
Enzymes
Other
Mechanisms of Enzyme Regulation
BOX 8-4 Regulation
of Protein Activity by Reversible Covalent Modification
Summary
Further Reading
Problems
