Enzyme Overview and Functions

Enzyme Overview

• Enzymes are biological catalysts
• They increase the rate of biochemical reactions
• They are highly specific for their substrate and reaction type
• Enzymes are not consumed in the reaction
• Most are proteins, some are ribozymes (RNA)
• Lower activation energy by stabilizing the transition state

Learning Objectives for Enzymes

• Describe enzymes and their properties
• List enzyme classifications
• Describe factors affecting enzyme activity
• Explain the relationship between Km and enzyme activity
• Explain enzyme inhibition and different types of inhibition

Metabolic Reactions and Enzymes

• Enzymes facilitate metabolic reactions, including both anabolic (building up) and catabolic (breaking down) pathways
• Enzymes increase the rate of these reactions, which are fundamental to life processes
• Enzymes catalyze reactions by lowering activation energy
• This speeds up reaction rates
• Enzymes can modify molecules by binding temporarily for transport, degradation, or modifications within cells.
• With some special molecules

Glycolysis Overview

• Glycolysis is a metabolic process that breaks down glucose into pyruvate
• Enzymes are crucial to facilitate these reactions (e.g., hexokinase, phosphofructokinase, etc.)
• Each reaction step is catalyzed by specific enzymes

Enzyme Activity

• Enzyme activity is the rate at which an enzyme catalyzes a reaction
• Measured by the amount of substrate converted to product in a given time
• One unit of enzyme activity converts 1 μmol of substrate to product in one minute under optimal conditions
• Enzyme activity is influenced by several factors, including enzyme concentration, substrate concentration, temperature, pH, and inhibitors.
• Enzyme activity can be measured and optimized according to these factors

Factors Affecting Enzyme Activity

• Enzyme concentration: Higher concentration, faster reaction
• Substrate concentration: More substrate, speeds reaction up until saturation
• Temperature: Optimal temperature for max efficiency; high temp, denatures/slows reactions
• pH: Affects enzyme structure and function (optimal pH for every enzyme)
• Inhibitors: Substrates that reduce enzyme rate.

Enzyme Nomenclature

• Enzymes are classified in an organized way
• This is done according to their function (i.e. oxidoreductases, transferases, hydrolases, etc.)
• Each enzyme is given a unique EC number for precise identification

Enzyme Kinetics and Km

• Km reflects the enzyme's affinity for its substrate
• Low Km means higher affinity (higher substrate concentration required to reach half V-max)
• High Km means lower affinity (requires high substrate concentration to get half Vmax)
• Vmax is the maximum reaction rate of an enzyme

Enzyme Regulation

• Factors influencing enzyme activity
• Enzymes can be regulated by changing the amount (synthesis/degradation), enzyme modification (e.g., phosphorylation / dephosphorylation), or the compartments in a cell.
• These factors influence enzyme activity at different stages/steps

Isoenzymes

• Enzymes that share the same catalytic function but have different structures(sequences) and different regulatory properties
• Examples include lactate dehydrogenase and creatine kinase
• Can be used to distinguish between different tissues or cellular conditions