Factors Affecting Enzyme Activity

Factors Affecting Enzyme Activity

• Enzyme activity is influenced by various factors
• Factors affecting enzyme activity include temperature, pH, time, concentration of coenzymes, concentration of ion activators, enzyme concentration, substrate concentration, and inhibitors.

Temperature Effects

• Reaction rate increases as temperature rises, up to a maximum at a specific temperature known as the optimum temperature
• Optimum temperature is when the maximum amount of substrate converts to products
• Optimal temperature for humans ranges between 37-40°C
• Increase in temperature initially increases the initial energy of the substrate, which decreases the activation energy, and increases the collision of molecules
• After the optimum temperature the reaction rate decreases due to enzyme denaturation (at 60-65°C)

pH Effects

• Each enzyme has an optimum pH at which its activity is highest
• Examples of enzymes and their optimum pH values:
  • Pepsin: 1.5-2
  • Pancreatic enzymes: 7.5-8
  • Salivary amylase: 6.8
• Optimal pH for most enzymes is 7.35-7.45
• Change in pH above or below optimal pH reduces enzyme activity due to ionization state changes of the enzyme and substrate active sites, potentially leading to denaturation

Time Effects

• In an enzymatically catalyzed reaction, the reaction rate decreases over time
• This can be due to:
  • Substrate depletion (exhaustion of substrate)
  • Accumulation of end products (which can cause feedback inhibition)
  • Change in pH away from the optimum pH

Coenzymes and Ion Activators

• Coenzymes: Increase in coenzyme concentration will increase the reaction rate in conjugated enzymes requiring coenzymes.
• Ion activators: An increase in metal ion activator concentration will increase the reaction rate

Enzyme Concentration

• The rate of an enzyme-catalyzed reaction is directly proportional to the enzyme concentration, given sufficient substrate and constant conditions

Substrate Concentration

• Reaction rate increases as substrate concentration rises until a maximum rate (Vmax) is reached
• At Vmax, the enzyme is saturated with substrate, and any further increase in substrate concentration does not affect the reaction rate

Enzyme Kinetics

• Enzyme kinetics studies the rate at which an enzyme acts
• Key concepts:
  • Michaelis constant (Km): The substrate concentration producing half the maximum velocity of the enzyme
  • High Km: low affinity of the enzyme for the substrate. The enzyme reaches maximum velocity only at high substrate concentrations
  • Low Km: high affinity for the substrate. The enzyme reaches maximum velocity even at low substrate concentrations

Enzyme Inhibitors

• Enzyme inhibitors reduce or stop enzyme activity.
• Types of enzyme inhibitors:
  • Competitive inhibitors
  • Non-competitive inhibitors

Summary of Factors Affecting Enzyme Activity

• Temperature, pH, time, coenzyme concentration, ion activator concentration, enzyme concentration, substrate concentration, and inhibitors all affect enzyme activity.
• Understanding these factors is crucial to controlling enzymatic reactions in biological systems