Enzyme Inhibition Flashcards by Elisha Long

What are chemicals that reduce the rate of enzymatic reactions?

Inhibitors

How well did you know this?

Not at all

Perfectly

What are two types of enzyme inhibitors?

Irreversible and reversible

How well did you know this?

Not at all

Perfectly

What type of inhibitor covalently modifies the active site of the enzyme irreversibly?

Irreversible

How well did you know this?

Not at all

Perfectly

What type of inhibitor can be washed out of the solution of enzyme by dialysis?

reversible

How well did you know this?

Not at all

Perfectly

What are the different types of reversible inhibitors?

1) Competitive
2) Uncompetitive
3) Non-competitive

How well did you know this?

Not at all

Perfectly

What are two different types of non-competitive inhibtors?

pure; mixed

How well did you know this?

Not at all

Perfectly

What residue does AchE use to prevent nerve gases and pesticides from getting utilized for catalysuis?

Serine

How well did you know this?

Not at all

Perfectly

Which type of inhibition does the inhibitor structure closely resemble the substrate’s structure and competes for the active site of the enzyme with the substrate?

Competitive

How well did you know this?

Not at all

Perfectly

Which type of inhibition does the inhibitor reduce the number of enzyme molecules available for the substrate?

Competitive

How well did you know this?

Not at all

Perfectly

Which type of inhibition does the inhibitor increase the km but not the overall velocity (vmax does not change)?

Competitive

How well did you know this?

Not at all

Perfectly

What is the equation for competitive inhibition?

vo=(Vmax[S])/(alphaKm + [S])

How well did you know this?

Not at all

Perfectly

What is the dissociation constant of EI in competitive inhibition?

Ki= [E][I]/[EI]

How well did you know this?

Not at all

Perfectly

What is alpha and what is its equation?

the degree of inhibition

alpha = 1 + ([I]/Ki)

How well did you know this?

Not at all

Perfectly

In competitive inhibition, the LB-plot slope increases as what increases?

the degree of inhibition (alpha)

How well did you know this?

Not at all

Perfectly

What example for competitive inhibition was given in class?

Methotrexate competitively inhibits dihydrofolate reductase (DHFR) (inhibits DNA synthesis)

HIV Protease Inhibitors (HIV Protease cleaves Phe-Pro bond

How well did you know this?

Not at all

Perfectly

How do you determine Ki for competitive inhibition?

1) plot I/vo vs 1/[S] (LB-plot) for different Is
2) find the slope of each line produced
3) plot the slope of the lines vs [I]
4) the x-intercept is -Ki (in concentration units)

How well did you know this?

Not at all

Perfectly

How do you overcome competitive inhibition?

by increasing the concentration of the substrate [S] Vmax can be attainable

How well did you know this?

Not at all

Perfectly

What example of overcoming competitive inhibition was given in class?

methanol or ethylene glycol poisoning, patients are given ethanol

methanol gets converted to formaldehyde instead of acetic acid (ethanol gets converted to acetic acid)

methanol is excreted in the urine if out-competed by ethanol

When this binds to an enzyme it completely distorts the active site rendering the enzyme catalytically innactive. What is it?

An uncompetitive enzyme

In uncompetititve inhibition, the inhibitor affects what but not what?

the catalytic function of the enzyme; the substrate binding

Vmax and km are reduced by the same extent in what type of inhibition?

Uncompetitive

What is the Michaelis-Menton equation for uncompetitive inhibition?

vo=(Vmax[S])/(Km+alpha’[S])

What is the dissociation constant for ESI?

K’i = ([ES][I])/[ESI]

What is the degree of inhibition for uncompetitive inhibition?

alpha’ = 1 + ([I]/K’i)

Does the slope change in uncompetitive inhibition?

Can the effect of the uncompetitive inhibitor be abolish by increasing [S]?

What was an example of an uncompetitive inhibitor given in class?

Round up- interferes with the synthesis of the aromatic amino acids

How do you find Ki for uncompetitive inhibition?

1. plot I/vo vs 1/[S] 2. plot the slopes of the lines formed vs [I] 3. -K'i = to the x-intercept

What kind of inhibitor can bind to the free enzyme as well as the enzyme/substrate complex and affects both substrate binding and catalysis?

Non-competitive

The non-competitive inhibitor binds to E and ES but may have a greater affinity for what?

one over the other

If the binding affinity of the non-competitive inhibitor to free enzyme equals the binding affinity to the enzyme/substrate complex, the inhibition is considered what?

Pure

If the binding affinity of the non-competitive inhibitor to free enzyme does not equal the binding affinity to the enzyme/substrate complex, the inhibition is considered what?

Mixed

If pure, alpha equals what?

alpha'

What is the Michaelis-Menton equation for non-competitive inhibition?

vo = to (vmax[S])/(alphaKm +alpha'[S])

With pure non-competitive inhibition, what happens to vmax, km, and the slope?

Vmax decreases, km remains the same, the slope changes

With mixed non-competitive inhibition, what happens to vmx, km, and the slope?

Vmax decreases, Km changes, the slope changes

What example of non-competitive inhibition was given in class?

Heavy metal poisoning

How do you find Ki and K'i for non-competitive inhibition?

1) LB plot (1/vo) vs 1/[S] at different [I] 2. plot the slopes of the LB plots vs [I] to find -Ki (x-intercept) 3) plot y-intercept vs [I} to find -K'i (x-intercept)

In which type of inhibition does vmax stay the same?

competitive

Does Vmax increase or decrease for uncompetitive and noncompetitive inhibition?

decrease

Does Km increase or decrease with competitive inhibition?

increase

Does Km increase or decrease with uncompetitive inhibition?

decrease

Does Km increase or decrease with non-competitive inhibition?

it can increase or decrease

In non-competitive inhibition, can the products formed by the inhibitor interact?

yes