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MFoM > 02c: Enzyme Kinetics and Inhibition > Flashcards

02c: Enzyme Kinetics and Inhibition Flashcards

1
Q

In unimolecular irreversible reaction, rate of P formation equals (X) and is directly proportional to (Y).

A

X = rate of A disappearance

Y = [A]

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2
Q

First order rate constant units.

A

1/s

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3
Q

Second order reaction rate constant units.

A

1/Ms

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4
Q

In unimolecular reversible reaction: large Keq favors (reactants/products).

A

Products

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5
Q

What’s the plot shape of substrate concentration versus reaction velocity in typical enzyme-catalyzed reaction?

A

Hyperbolic

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6
Q

Zero order reaction is found at what substrate concentration? The reaction velocity equals:

A

When [S] much greater (20x) Km

Vo = Vm

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7
Q

List Michaelis-Menten assumptions.

A
  1. ES forms
  2. No back reaction
  3. Initial v used
  4. [ES] in steady state
  5. Negligible substrate depletion
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8
Q

How does a larger Km affect the plot/curve shape?

A

Flattens out curve

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9
Q

Kd is known as (X) and tells you about (Y).

A 
X = dissociation constant
Y = binding affinity
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10
Q

Small Km is indicative of (strong/weak) binding.

A

Strong

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11
Q

Kcat is formally termed:

A

Turnover number

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12
Q

Catalytic efficiency of enzyme represented by:

A

Kcat/Km

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13
Q

What defines a “perfect enzyme”?

A

Kcat/Km in range of

10(^8) - 10(^9)

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14
Q

Units for catalytic efficiency:

A

1/Ms

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15
Q

It’s recommended to use (linear/nonlinear) regression of data to determine Km and Vm.

A

Nonlinear (hyperbolic)

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16
Q

Is it possible to linearize Michaelis-Menten?

A

Yes - take reciprocal of both sides to get Lineweaver-Burk plot

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17
Q

Lineweaver-Burk plot slope represents:

A

Km/Vm

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18
Q

Lineweaver-Burk plot x-intercept represents:

A

-1/Km

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19
Q

Lineweaver-Burk plot y-intercept represents:

A

1/Vm

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20
Q

Increasing Vm will have what effect on Lineweaver-Burk plot?

A

Bring y-intercept closer to origin

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21
Q

Increasing Km will have what effect on Lineweaver-Burk plot?

A

Bring X-intercept closer to origin

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22
Q

A “perfect enzyme” will have what difference in Lineweaver-Burk plot compared to another enzyme?

A

Smaller slope

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23
Q

Can Kcat be determined from (michaelis-menten/lineweaver-Burke) plot? What’s the equation?

A

Either, as long as [E]t and Vmax are determined;

Vm = Kcat*[E]t

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24
Q

Bi-substrate reaction classes:

A
  1. Sequential

2. Ping-pong

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25
Q

All substrates bind in specific order before any product released describes which bi-substrate reaction class?

A

Sequential (ordered)

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26
Q

All substrates bind randomly before any product released describes which bi-substrate reaction class?

A

Sequential (random)

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27
Q

One substrate binds and releases product before second substrate binds describes which bi-substrate reaction class?

A

Ping-pong (double-displacement)

28
Q

(Competitive/uncompetitive/non competitive) inhibitors are irreversible.

A

None - all are reversible

29
Q

Competitive inhibitors bind to:

A

Free enzyme only

30
Q

T/F: competitive inhibitors don’t affect the amount of ES complex formed.

A

False

31
Q

How does Km change in presence of competitive inhibitor.

A

It doesn’t! Only apparent value changes

32
Q

How does apparent Km value change in presence of competitive inhibitor?

A

Increase

33
Q

How does apparent Vm value change in presence of competitive inhibitor?

A

No change

34
Q

How does apparent catalytic activity value change in presence of competitive inhibitor?

A

Decrease

35
Q

Uncompetitive inhibitors bind to:

A

ES complex only (not at active site)

36
Q

How does uncompetitive inhibitor hinder reaction?

A

Distorts active site, making it catalytically inactive

37
Q

How does apparent Vm value change in presence of uncompetitive inhibitor?

A

Decreases

38
Q

How does apparent Km value change in presence of uncompetitive inhibitor?

A

Decreases

39
Q

How does apparent catalytic activity value change in presence of uncompetitive inhibitor?

A

No change

40
Q

At low [S], which inhibitor(s) decrease rate?

A

Competitive and Noncompetitive

41
Q

At low [S], which inhibitor(s) don’t change rate?

A

Uncompetitive

42
Q

Noncompetitive inhibitors bind to:

A

Free enzyme or ES complex

43
Q

Do (X) inhibitors bind with greater Ki to free enzyme or ES complex?

A

X = non-competitive

Bind with same Ki to either

44
Q

How does noncompetitive inhibitor hinder reaction?

A

Distorts enzyme structure, preventing alignment of catalytic center

45
Q

How does apparent Vm value change in presence of noncompetitive inhibitor?

A

Decreases

46
Q

How does apparent Km value change in presence of noncompetitive inhibitor?

A

No change

47
Q

How does apparent catalytic activity value change in presence of noncompetitive inhibitor?

A

Decreases

48
Q

Enzymatic activity can be precisely regulated in which ways?

A
  1. Allosteric control
  2. Regulatory proteins
  3. Reversible covalent modifications
  4. Proteolytic activity
49
Q

Allosteric enzymes do not obey (X) because the [S] v. Vo plot has which shape?

A

X = michaelis-menten kinetics

Sigmoidal shape

50
Q

Sigmoidal curves result from (X) cooperativity, indicating which change in Km?

A

X = positive

Decrease Km with increase in [S]

51
Q

In allosteric control, (X) effector is same as substrate and (Y) effector is different from substrate.

A 
X = homotropic
Y = heterotropic
52
Q

Does allosteric control change Km or Vm?

A

Can change either or both

53
Q

Are allosteric enzymes monomeric or oligomeric?

A

Can be either

54
Q

ATCase is an enzyme that catalyzes:

A

first step in pyrimidine biosynthesis pathway

55
Q

(X) is a negative effector of the ATCase enzyme.

A

X = CTP

56
Q

Describe structure of ATCase.

A

6 catalytic subunits (trimers) and 6 regulatory subunits (dimers)

57
Q

ATCase is in equilibrium between which two states? Which is favored?

A

Tense and relaxed;

Tense favored (200:1)

58
Q

(X), the ATCase substrate, stabilizes which of the two enzyme states?

A

X = aspartate

Relaxed state

59
Q

The final product of ATCase pathway, (X), stabilizes which of the two enzyme states?

A

X = CTP

Tense state

60
Q

Name a positive effector of ATCase.

A

ATP

61
Q

The positive/negative effectors of ATCase bind which subunits on enzyme?

A

Regulatory

62
Q

Give example of reversible, covalent modifications of enzymes.

A

Phosphorylation and de-phosphorylation

63
Q

T/F: Phosphorylation always increases enzyme activity.

A

False

64
Q

Kinases (add/remove) (X) groups to/from proteins using:

A

Add
X = phosphate

ATP

65
Q

Phosphatases (add/remove) (X) groups to/from proteins using:

A

Remove
X = phosphate

H2O (hydrolysis)

MFoM (20 decks)

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