enzymes ii - oregon state...
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Kinetic Considerations
Pre-steady state
[E] and [ES] varying widely
Steady state
[E] and [ES] relatively constant
Enzymes• Kinetic Considerations
Initial Velocity (V0) - Measured as [Product]/Time
Substrate Concentration (Molarity)
Enzymes• Kinetic Considerations
Low [S], Low V0 (Enzymes Often Idle)
High [S], High V0 (Enzymes Almost Always Busy)
Michaelis-‐Menten Kinetics• Parameters
Km
Km = Substrate Concentration that Gives Vmax/2 NOT Vmax/2
Michaelis-‐Menten Kinetics• Parameters
Km
Km = Substrate Concentration that Gives Vmax/2 NOT Vmax/2
Michaelis-‐Menten Kinetics• Considerations
v0 = Vmax[S]Km + [S]
Enzymes That Don’t Follow Michaelis-Menten Kinetics Include Those That Bind Substrate Cooperatively - Binding of One Substrate Affects Binding of Others
Control of Enzyme Activity• Allosteric Control
Substrate Does Not Change Enzyme Binding of Substrate
Control of Enzyme Activity• Allosteric Control
Substrate Does Not Change Enzyme Binding of Substrate Substrate Does Change Enzyme
Binding of Substrate
Michaelis-‐Menten Equation
Vmax occurs when an enzyme is saturated by substrateVmax varies with amount of enzyme used
Michaelis-‐Menten Equation
Vmax occurs when an enzyme is saturated by substrateVmax varies with amount of enzyme usedKm is a measure of an enzyme’s affinity for its substrate
Michaelis-‐Menten Equation
Vmax occurs when an enzyme is saturated by substrateVmax varies with amount of enzyme usedKm is a measure of an enzyme’s affinity for its substrateKm value inversely related to affinity
Michaelis-‐Menten Equation
Vmax occurs when an enzyme is saturated by substrateVmax varies with amount of enzyme usedKm is a measure of an enzyme’s affinity for its substrateKm value inversely related to affinity
High Km = Low Affinity Low Km = High Affinity
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
Since Vmax is a Velocity, and Velocity = [Product]/Time,
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax
[Enzyme Used]= [Product]
[Enzyme Used] *Time
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
Since Vmax is a Velocity, and Velocity = [Product]/Time,
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax
[Enzyme Used]= [Product]
[Enzyme Used] *Time
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
The Two Concentrations Cancel Out.
Since Vmax is a Velocity, and Velocity = [Product]/Time,
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax
[Enzyme Used]= [Product]
[Enzyme Used] *Time
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
The Two Concentrations Cancel Out. The Result is a Number Per time (say 1000/second).
Since Vmax is a Velocity, and Velocity = [Product]/Time,
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax
[Enzyme Used]= [Product]
[Enzyme Used] *Time
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
The Two Concentrations Cancel Out. The Result is a Number Per time (say 1000/second).
It is the Number of Product Molecules Made by Each Enzyme Molecule Per Time.
Since Vmax is a Velocity, and Velocity = [Product]/Time,
Michaelis-‐Menten Kinetics• Vmax and Kcat
Vmax
[Enzyme Used]= [Product]
[Enzyme Used] *Time
Vmax is Proportional to the Amount of Enzyme Used in an Experiment - Not Useful for Comparing Enzymes
The Two Concentrations Cancel Out. The Result is a Number Per time (say 1000/second).
It is the Number of Product Molecules Made by Each Enzyme Molecule Per Time. It is Also Known as the Turnover Number or Kcat and
Does Not Vary with the Amount of Enzyme
Since Vmax is a Velocity, and Velocity = [Product]/Time,
Michaelis-‐Menten Kinetics• Lineweaver Burk Plot
Also Called Double Reciprocal Plot Uses Same Data as V vs. [S] Plot, but Inverts All Data for the Plotting
Michaelis-‐Menten Kinetics• Lineweaver Burk Plot
Also Called Double Reciprocal Plot Uses Same Data as V vs. [S] Plot, but Inverts All Data for the Plotting
Linear for Enzymes Following Michaelis Menten Kinetics
Michaelis-‐Menten Kinetics• Lineweaver Burk Plot
Also Called Double Reciprocal Plot Uses Same Data as V vs. [S] Plot, but Inverts All Data for the Plotting
Direct Reading of -1/Km and 1/Vmax
Michaelis-‐Menten Kinetics• Lineweaver Burk Plot
Also Called Double Reciprocal Plot Uses Same Data as V vs. [S] Plot, but Inverts All Data for the Plotting
Direct Reading of -1/Km and 1/Vmax
Enzymes (To the tune of "Downtown")
Copyright Kevin Ahern
Enzymes (To the tune of "Downtown")
Copyright Kevin Ahern Reactions alone Could starve your cells to the bone Thank God we all produce Enzymes Units arrange To make the chemicals change Because you always use Enzymes
Sometimes mechanisms run like they are at the races Witness the Kcat of the carbonic anhydrases
How do they work? Inside of the active site It just grabs onto a substrate and squeezes it tight In an ENZYME! CAT-al-y-sis In an ENZYME! V versus S In an ENZYME! All of this working for you
Energy peaks Are what an enzyme defeats In its catalysis Enzymes
Transition state Is what an enzyme does great And you should all know this Enzymes
Catalytic action won't run wild - don't get hysteric Cells can throttle pathways with an enzyme allosteric
You know it's true So when an effector fits It will just rearrange all the sub-u-nits Inside an ENZYME! Flipping from R to T ENZYME! Slow catalytically ENZYME! No change in Delta G
You should relax When seeking out the Vmax though There are many steps Enzymes Lineweaver Burk Can save a scientist work With just two intercepts Enzymes
Plotting all the data from kinetic exploration Lets you match a line into a best fitting equation Here's what you do Both axes are inverted then You can determine Vmax and Establish Km for your ENZYMES! Sterically holding tight ENZYMES! Substrates positioned right ENZYMES! Inside the active site Enzymes (Enzymes, enzymes, enzymes)
Enzymes (To the tune of "Downtown")
Copyright Kevin Ahern Reactions alone Could starve your cells to the bone Thank God we all produce Enzymes Units arrange To make the chemicals change Because you always use Enzymes
Sometimes mechanisms run like they are at the races Witness the Kcat of the carbonic anhydrases
How do they work? Inside of the active site It just grabs onto a substrate and squeezes it tight In an ENZYME! CAT-al-y-sis In an ENZYME! V versus S In an ENZYME! All of this working for you
Energy peaks Are what an enzyme defeats In its catalysis Enzymes
Transition state Is what an enzyme does great And you should all know this Enzymes
Catalytic action won't run wild - don't get hysteric Cells can throttle pathways with an enzyme allosteric
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