Lecture 3

What Does Optimal Conditions for Enzymatic Activity Mean?

OPTIMAL ENVIRONMENT where an enzyme functions

Why Do Optimal Conditions Maximize Enzyme Activity

• FAVORS enzyme’s most active shape

  • Allows it to function effectively

Different Parts of Enzyme Lab 3

• PART 4 → Reaction Temperatures

• PART 5 → Boil/Freezing Enzyme

• PART 6 + 7 → Inhibitors

• PART 8 → Cofactors

• PART 9 → Salt

Different Types of Enzyme Inhibitors

• Competitive Inhibitors

• Noncompetitive Inhibitors

Competitive Inhibitors

• Bind to ACTIVE SITE

• COMPETES with substrate

Noncompetitive Inhibitors

• Binds to ANOTHER PART if enzyme (allosteric site)

• CHANGES shape of enzyme

  • Makes it LESS effective

Non-Specific Inhibition

• Inhibition that affects ALL enzymes in the SAME WAY

  • EXAMPLES: Environmental factors, chemical denaturants, etc.

How Does Competitive Inhibition Affect V_max?

• STAYS THE SAME

  • High substrate concentration can OUTCOMPETE inhibitor

How Does Competitive Inhibition Affect K_m?

• INCREASES

  • Higher substrate concentration NEEDED to reach half of V_max

How Does Noncompetitive Inhibition Affect V_max?

• DECREASES

  • FEWER functional enzymes available to catalyze reaction

How Does Noncompetitive Inhibition Affect K_m?

• MAY OR MAY NOT CHANGE

  • Inhibitor CAN POTENTIALLY change enzyme’s affinity for substrate

What is V_max?

• MAXIMUM rate of reaction

• ALL enzyme active sites are FULL (saturated)

What is K_m?

• AFFINITY (attraction) of enzyme for substrate

• SUBSTRATE CONCENTRATION at which reaction rate is HALF of V_max

Percent Inhibition Formula

(Rate w/out Inhibitor - Rate w/Inhibitor) / (Rate w/ Inhibitor)

Percent Inhibition Definition

• The percent DECREASE in enzyme activity

  • CAUSED by an inhibitor

  • COMPARED to control without inhibitor

How Does Percent Inhibition by Competitive Inhibitor Change with Substrate Concentration?

• CHANGES at DIFFERENT substrate concentrations

• Example:

  • Low Substrate → 50%

  • High Substrate → 10%

How Does Percent Inhibition by Noncompetitive Inhibitor Change with Substrate Concentration?

• STAYS THE SAME for ALL substrate concentrations

• Example:

  • Low Substrate → 50%

  • High Substrate → 10%

Cofactors Definition

NONPROTEIN enzyme helpers

What do Cofactors Do?

• HELP enzymes function properly

  • ASSIST with catalysis (bind or carry out reaction)

• TIGHTLY CONTROL enzyme function

• EXAMPLE: metal ions, vitamins

Different Types of Cofactors

• Inorganic (e.g. metal ions)

• Organic (e.g. vitamins)

How Does a Chelator Inhibit Enzyme Function?

• “CHEMICAL CLAW”

• BINDS and removes metal ions from solution

• PREVENTS enzymes that require those ions (cofactors) from functioning properly

What does a higher V_max mean?

• HIGHER maximum reaction rate

• Enzyme can produce product FASTER when substrate abundant

What does a lower K_m mean?

• LESS substrate needed to reach half of V_max

• INDICATING higher substrate affinity