Biochemistry - Lecture 9: Saturation Kinetics & Reaction Rate Acceleration by Enzymes

enzyme concentration

Reaction kinetics are dependent upon ________________________

excess substrate

At a fixed concentration, enzymes can be saturated with __________________________

The Michaelis constant - Km

What is 1/2 of Vmax?

V0 = Vmax[S] / Km + [S]

What is the Michaelis-Menten Equation?

Km = (k-1 + k2) / k1)

What is the equation for calculating Km?

v0 = Vmax[S] / Km

Also called specificity constant (kcat/Km)

What is V0 if [S] << Km?

V0 = Vmax

What is V0 if [S] >> Km?

dissociation constant for the ES complex and affinity of E for S

->smaller Km = higher affinity

When k2 << k1, what does Km represent?

AKA turnover number

How many substrate molecules one enzyme can convert per second

For most enzymes, kcat ≈ k2

What is the kcat?

Vmax

The asymptote of a hyperbolic curve when V0 is plotted against [S]

AKA the fastest a given concentration of enzymes can catalyze a reaction

What is the maximal velocity?

Kcat/Km - best method for comparing enzyme efficiency

What is the specificity constant?

AKA specificity constant

Revealed by Kcat/Km

What is catalytic efficiency?

How efficiently an enzyme speeds up a reaction comparted to the reaction without the enzyme

Determined by (Kcat/Km) / k(uncat)

What is catalytic proficiency?

y axis: 1/V0

x axis: 1/[S]

What are the x and y axis on the Lineweaver-Burk plots?

1/Vmax

What is the y-intercept of the Lineweaver-Burk plot?

- 1/Km

What is the x-intercept of the Lineweaver-Burk plot?

Km/Vmax

What is the slope of a line on the LWB plot?

Sequential displacement

Double-displacement

What are the two classes of reactions with multiple substrates?

Substrates bind to the protein in a certain order

What is ordered sequential displacement?

Substrates bind to protein in a random order

What is random sequential displacement?

Intersect

A Lineweaver-Burk Plot with a sequential mechanism will have lines of varying [S2] _____________________________________

y-axis

Random mechanisms in equilibrium will give intersections point at _________________________

AKA ping-pong

Temporary formation of a substituted enzyme

What is double displacement?

Parallel to each other

A Lineweaver-Burk Plot with a double displacement mechanism will have lines of varying [S2] _____________________________________

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