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IMS > ENZYMES IN DISEASES > Flashcards

ENZYMES IN DISEASES Flashcards

1
Q

what are enzymes?

A

biological catalysts

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2
Q

what do enzymes enable?

A

enable reactions to take place in living material that would otherwise occur only very slowly or only under very harsh conditions

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3
Q

what is the function of enzymes?

A

speed up the attainment of equilibrium of a reaction without altering the final equilibrium position

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4
Q

are enzymes specific?

A

yes

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5
Q

why are reactions that enzymes catalyse specific?

A

because the composition of the active site is characteristic of a single enzyme catalysing a specific reaction

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6
Q

what causes enzymes to be specific?

A

Only the correct substrate will bind to the active site

The specificity of binding depends on the shape of the substrate and enzyme molecule

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7
Q

do enzymes have a high or low molecular mass?

A

high

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8
Q

what is the amount of enzyme needed in a reaction?

A

very small

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9
Q

how is an enzyme recognised?

A

by its activity, and the initial velocity (v0) of the reaction catalysed is what we can easily measure

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10
Q

define units of enzymes

A

the amount of enzyme which will catalyse the transformation of
1 μmol of substrate to product in 1 min

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11
Q

what does damage to cells by acute disease lead to?

A

increases the permeability of the cell memb, so that cytoplasmic enzymes, like lactate dehydrogenase, leak out into the circulation and their activity can be detected in serum

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12
Q

why is the measurement of the amount of lactate dehydrogenase in the serum important?

A

it is of clinical importance in diagnosis and prognosis

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13
Q

After myocardial infarction does the serum lactate dehydrogenase rise or fall?

A

rises

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14
Q

what are the factors affecting the rate of an enzyme catalysed reaction?

A 
Enzyme conc
Substrate conc
pH
Temperature
Inhibitors
Coenzymes, cofactors, 	prosthetic groups
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15
Q

what is Vmax?

A

the maximum velocity (rate) of the reaction. It occurs at saturating [S]

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16
Q

what is Km?

A

the Michaelis constant

It is equal to the substrate conc at which the rate is half of the maximum rate, Vmax.

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17
Q

what is Km a measure of?

A

affinity of the E for S and is the [S] needed to achieve half Vmax

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18
Q

what have high Km values?

A

Enzymes with low affinities for their substrate

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19
Q

what have low Km values?

A

Enzymes with high affinities for their substrate

20
Q

what does an inhibitor do?

A

binds to the enzyme and prevents it from being active

21
Q

what are inactivators?

A 
Very tightly (irreversibly) bound inhibitors 
they stop the enzyme-catalysed reaction Initial velocity v0 is zero.
22
Q

what do reversibly bound inhibitors do?

A

reduce the initial velocity, v0, according to how much of it is bound

23
Q

what are the 2 types of reversibly-bound inhibitors?

A

competitive

non-competitive

24
Q

how do competitive inhibition work?

A

both the substrate, S, and the inhibitor, I, bind to the same site on the enzyme, the active site

25
Q

what happens at very high conc of substrate?

A

they will displace all of the inhibitor from the active site, so there is no inhibition and the Vmax is unchanged from the non-inhibited case

26
Q

what is the Lineweaver Burk plot?

A

used to determine the type inhibition caused

27
Q

give an example of a competitive inhibitor

A

Methotrexate

28
Q

what is methotrexate?

A

an anti-cancer drug. It is a structural analogue of tetrahydrofolate It inhibits the enzyme Tetrahydrofolate Reductase, involved in purine and pyrimidine synthesis

29
Q

what does non-competitive inhibition involve?

A

Inhibitor binds at a different site to the substrate.

Inhibitor can bind to E or ES equally well.

30
Q

in non-competitive inhibition does the binding of S change?

A

no, but the enzyme can no longer transform the substrate to the product as efficiently
Vmax is decreased

31
Q

give an example of a non-competitive inhibitor

A

Deoxycycline

32
Q

what is Deoxycycline?

A

inhibitor of the enzyme Collagenase.
It covalently binds to this enzyme.
Collagenase is a bacterial proteolytic enzyme which damages the gums.
Inactivation of this enzyme is used to treat peridontal disease.

33
Q

what do competitive inhibitors compete with?

A

compete with the substrate for binding to the active site of the enzyme, reducing the affinity of enzyme for its substrate

34
Q

how is Vmax effected in competitive inhibitors?

A

unaltered

35
Q

how is Km effected in competitive inhibitors?

A

increased

36
Q

where do non-competitive inhibitors bind?

A

at a site distant from the active site, causing a change in shape of the enzyme
reducing its effectiveness at converting substrate to product

37
Q

how is Vmax effected in non-competitive inhibitors?

A

reduced

38
Q

how is Km effected in non-competitive inhibitors?

A

unaltered

39
Q

what is irreversible inhibition?

A

binds irreversibly and forms covalent bonds to AA residues at or near the active site

40
Q

what does irreversible inhibition do?

A

alters the shape of the enzyme causing it to lose its biological activity
Permanently inactivates the enzyme

41
Q

give examples of irreversible inhibitors

A

penicillin

aspirin

42
Q

what is penicillin?

A

covalently binds to the enzyme Transpeptidase, which synthesises cross links in some bacterial cell walls
Inactivating this enzyme prevents the synthesis of new bacterial cell walls so kills off a bacterial infection

43
Q

what does MRSA stand for?

A

Methicillin-Resistant Staphylococcus Aureus

44
Q

what is MRSA?

A

β-lactam antibiotic

45
Q

what is aspirin?

A

covalently binds to Cyclo-oxygenase(COX) enzymes, which add oxygen molecules to unsaturated fatty acids during the synthesises of prostaglandin

IMS (52 decks)

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