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Flashcards in enzyme regulation Deck (42):
1

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

-cause conformational change that affects catalysis
-alter cell localization of enzyme
-alter interactions with other proteins

2

glycogen phosphorylase is an example of what type of regulation?

reversible covalent modification

3

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

regulation of irreversible covalent modification

4

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

irreversible enzyme activations

5

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

-rapid activation of blood coagulation
-localization of clot to site of injury
-rapid termination after clot formation to prevent thrombosis

6

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

serine proteases

7

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

reversible covalent modification

8

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

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

9

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

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

10

how is the clotting cascade terminated?

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

11

how does plasmin work?

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

12

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

TPA (tissue plasminogen activator)

13

what is the action of pancreatic trypsin inhibitor?

substrate that binds very tightly to the active site of trypsin

14

what is the action of alpha-antitrypsin

inhibitor of elastase-protects tissues from elastase secreted by neutrophils

15

what type of inhibitor is anti-thrombin?

serpin-serine protease inhibitor

16

how does the presence of heparin effect ATIII

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

17

what characterizes an ATIII deficiency/

excessive clotting (thrombosis) often in legs and lungs

18

list some characteristics of a1-antitrypsin deficiency

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

How is protein kinase A regulated?

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

20

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

Rate of product formation over time

21

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

-EXCESS SUBSTRATE

22

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

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

When would a coupled enzyme assay be used?

When direct measurement of the specific products is not possible

24

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

Substrates for BOTH of the reactions taking place

25

What is the goal of performing a coupled enzyme assay?

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

26

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

-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

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

-excess ENZYMES and other substrates involved in the reaction

28

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

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

29

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

-damage to tissue of origin
-spillover due to overproduction
-tumor

30

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

-level of enzyme activity
-timing of appearance of activity
-presence of tissue-specific isozymes

31

What does alanine aminotransferase - ALT in the plasma mean?

Viral hepatitis

32

What does amylase in the plasma mean?

acute pancreatitis

33

What does creatine kinase in the plasma mean?

-MI
-muscle disorders

34

What does LDH 5 in the plasma mean?

-Liver diseases

35

What does lipase in the plasma mean

acute pancreatitis

36

What does phophatase acid in the plasma mean?

Metastatic carcinoma of the prostate

37

What does phosphatase alkaline isozymes in the plama mean?

-Various bone disorders
-obstructive liver disease

38

What three enzymes in the plasma indicate MI?

-CK2
-LDH1
-aspartate aminotransferase AST

-These all appear transiently after an MI

39

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

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

40

What is the definition of an isozyme?

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

41

How can different isozymes be distinguished?

-charge difference - electrophoresis
-specific monoclonal antibodies
-differences in enzymatic properties or inhibitor sensitivities

42

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

-CK3
-long term rise in plasma CK over weeks