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Enzymes > enzyme regulation > Flashcards

enzyme regulation Flashcards

1
Q

what are the 3 ways you can regulate an enzyme by reversible covalent modification?

A
  • cause conformational change that affects catalysis
  • alter cell localization of enzyme
  • alter interactions with other proteins
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2
Q

glycogen phosphorylase is an example of what type of regulation?

A

reversible covalent modification

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3
Q

zymogens becoming activated by cleavage by another protease go onto synthesize and activate other enzymes. what type of regulation is this an example of?

A

regulation of irreversible covalent modification

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4
Q

maintenance of blood clotting cascade is an example of what type of regulation?

A

irreversible enzyme activations

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5
Q

what three rapid responses are needed to maintain blood volume following a blood vessel injury?

A
  • rapid activation of blood coagulation
  • localization of clot to site of injury
  • rapid termination after clot formation to prevent thrombosis
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6
Q

what is the classification of most of the enzymes in most of the blood clotting cascade?

A

serine proteases

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7
Q

localization of the clot in the coagulation cascade is what type of regulation?

A

reversible covalent modification

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8
Q

what part of the coagulation cascade is vitamin K involved in?

A

the localization of the clot to site of injury

it is a co-factor for the enzyme that catalyzes the addition of the y-carboxyl group

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9
Q

how does coumadin and warfarin (anti-coag drugs) act on the coagulation cascade?

A

they mimic vit K so they are able to get into and act as competitive inhibitors to enzymes that would normally be involved in the y-carboxyglutamate modification step

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10
Q

how is the clotting cascade terminated?

A

by an opposing cascade involving another serine protease-plasmin. “reverse zymogen activation cascade”

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11
Q

how does plasmin work?

A

by hydrolyzing peptide bonds in the fibrin clot, breaking it up

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12
Q

what serine protease can be administered after the onset of MI symptoms?

A

TPA (tissue plasminogen activator)

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13
Q

what is the action of pancreatic trypsin inhibitor?

A

substrate that binds very tightly to the active site of trypsin

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14
Q

what is the action of alpha-antitrypsin

A

inhibitor of elastase-protects tissues from elastase secreted by neutrophils

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15
Q

what type of inhibitor is anti-thrombin?

A

serpin-serine protease inhibitor

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16
Q

how does the presence of heparin effect ATIII

A

ATIII binds very poorly to the proteases (which cleaves it so that it can go onto irreversibly inhibit an enzyme) unless heparin is present

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17
Q

what characterizes an ATIII deficiency/

A

excessive clotting (thrombosis) often in legs and lungs

18
Q

list some characteristics of a1-antitrypsin deficiency

A

too much active elastase in lung eventually causes COPD
patient cant inhibit elastase and is plagued with SOB
severe deficiency is often accompanied by liver disease

19
Q

How is protein kinase A regulated?

A

Interaction of cAMP with regulatory subunits - releases inhibition by regulatory subunits and activates catalysis

20
Q

In order to determine how much enzyme is present, what data do clinical labs usually use?

A

Rate of product formation over time

21
Q

In an assay measuring product, what would be added in excess?

A

-EXCESS SUBSTRATE

22
Q

Why do we measure the rate of the rxn at saturating substrate concentration if we want to determine how much enzyme is present?

A

Because at the Vmax (saturating substrate concentration) - the rate of the rxn is directly proportional to the amount of enzyme present

-[detla S] and [delta P] are linear

23
Q

When would a coupled enzyme assay be used?

A

When direct measurement of the specific products is not possible

24
Q

In a coupled enzyme assay, what should be added in excess?

A

Substrates for BOTH of the reactions taking place

25
Q

What is the goal of performing a coupled enzyme assay?

A

You are measuring the products of the second reaction in order to calculate the amount of enzyme present in the first reaction

26
Q

When measuring metabolites or drug levels, what is the goal of the assay?

A
  • You must use an enzyme specific to that small molecule in the complex mixture
  • You are measuring the amount of product formed to quantitate this substance
27
Q

What would you add in excess to a metabolite or drug level enzyme assay?

A

-excess ENZYMES and other substrates involved in the reaction

28
Q

In a blood glucose coupled enzyme assay, what is detected and how?

A

NADPH by its ability to reduce a colored dye to form a colored product - dipstick

29
Q

Why do non-plasma specific enzymes appear in the plasma?

A
  • damage to tissue of origin
  • spillover due to overproduction
  • tumor
30
Q

How are non-plasma specific enzymes detected in the plasma?

A
  • level of enzyme activity
  • timing of appearance of activity
  • presence of tissue-specific isozymes
31
Q

What does alanine aminotransferase - ALT in the plasma mean?

A

Viral hepatitis

32
Q

What does amylase in the plasma mean?

A

acute pancreatitis

33
Q

What does creatine kinase in the plasma mean?

A
  • MI

- muscle disorders

34
Q

What does LDH 5 in the plasma mean?

A

-Liver diseases

35
Q

What does lipase in the plasma mean

A

acute pancreatitis

36
Q

What does phophatase acid in the plasma mean?

A

Metastatic carcinoma of the prostate

37
Q

What does phosphatase alkaline isozymes in the plama mean?

A
  • Various bone disorders

- obstructive liver disease

38
Q

What three enzymes in the plasma indicate MI?

A
  • CK2
  • LDH1
  • aspartate aminotransferase AST

-These all appear transiently after an MI

39
Q

What else is important besides the presence of certain enzymes in the plasma to diagnose an MI?

A

The timing of their rise and fall - need to measure the enzyme levels at multiple times

40
Q

What is the definition of an isozyme?

A

Different forms of an enzyme that carry out the same reaction - they have different AA sequences, chemical properties and enzymatic characteristics

41
Q

How can different isozymes be distinguished?

A
  • charge difference - electrophoresis
  • specific monoclonal antibodies
  • differences in enzymatic properties or inhibitor sensitivities
42
Q

What enzymes would be present in the plasma in a patient with muscular dystrophy?

A
  • CK3

- long term rise in plasma CK over weeks

Enzymes (4 decks)

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