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The Medicine (Y2) > Enzyme inhibitors > Flashcards

Enzyme inhibitors Flashcards

1
Q

Irreversible inhibitors act at the active site of an enzyme only. True or false?

A

False - at active site or remote from it

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2
Q

An excess of substrate can displace irreversible inhibitors. True or false?

A

False

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3
Q

Cephalosporins are examples of reversible inhibitors. True or false?

A

False - irreversible

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4
Q

Proton pump inhibitors are irreversible inhibitors. True or false?

A

True

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5
Q

Is orlistat a reversible or irreversible inhibitor?

A

Irreversible

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6
Q

Reversible inhibitors bind by intermolecular interactions rather than covalent bonds. True or false?

A

True

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7
Q

Increasing substrate concentration reverses inhibition of reversible inhibitors. True or false?

A

True

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8
Q

Are anti-depressants reversible or irreversible enzyme inhibitors?

A

Reversible

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9
Q

Are ACE inhibitors reversible or irreversible enzyme inhibitors?

A

Reversible

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10
Q

Are statins reversible or irreversible enzyme inhibitors?

A

Reversible

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11
Q

Competitive inhibitors are usually reversible under what circumstance?

A

If the concentration of substrate is sufficient enough to displace the inhibitor

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12
Q

For competitive inhibitors, the inhibition depends on three things. What are they?

A

The concentration of inhibitor
The concentration of the substrate
The relative affinities of the substrate and inhibitor for the active site of the enzyme

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13
Q

A non-competitive inhibitor inhibits at the active site of the enzyme. True or false?

A

False - adjacent to or distant from the active site

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14
Q

Are non-competitive inhibitors influenced by substrate concentration?

A

No

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15
Q

What is Kcat?

A

Overall rate constant for the decomposition of ES complex into products

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16
Q

Substrate analogues and product mimics are ______ ______ inhibitors

A

ground state

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17
Q

Suicide inhibitors and transition state analogues are _______ ______ inhibitors

A

mechanism based

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18
Q

Methotrexate is a competitive reversible inhibitor. True or false?

A

True

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19
Q

Methotrexate has a higher affinity for DHFR than FH2 does. True or false?

A

True - due to the additional hydrogen and ionic bonds in methotrexate

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20
Q

How does methotrexate work in cancer therapy?

A

It is a competitive reversible inhibitor and so binds to DHFR stopping the pathway to production of N5,N10-methylene-FH4 and so this means there is no source of methyl for production of dTMP = no DNA synthesis and therefore no cell division

21
Q

Methotrexate has a similar structure to FH2. True or false?

A

True

22
Q

In product mimicking - the final product of the pathway controls the enzyme with the allosteric site. True or false?

A

True

23
Q

Anti-purine is a product mimic. How does it work as an anti-cancer drug?

A

It is an analogue of the final product in purine biosynthesis. It is an allosteric inhibitor of an early enzyme in purine biosynthesis

24
Q

6-Mercaptopurine is a prodrug. How does it work as an anti-cancer drug?

A

It is converted into its corresponding nucleoside mono-phosphate and inhibits the first enzyme in the biosynthesis of purine

25
Q

Product analogues are reversible competitive inhibitors True or false?

A

False - reversible non-competitive

26
Q

Which three amino acids posses nucleophilic residues that can be attacked by an electrophilic drug to form a covalent bond in irreversible non-competitive inhibition?

A

Cysteine
Serine
Histidine

27
Q

What are the three types of irreversible inhibitors?

A

Suicide inhibitors
Affinity labels
Group-specific reagents

28
Q

What are group specific reagents?

A

React with specific AA side chains

29
Q

What are affinity labels?

A

Reactive substrate analogues
Structurally similar to substrate
Capable of covalently binding to active site

30
Q

Affinity labels are more specific than group specific reagents. True or false?

A

True

31
Q

Which drug is an irreversible inhibitor or pancreatic lipase?

A

Orlistat

32
Q

Irreversible inhibitors are highly reactive. True or false?

A

True

33
Q

The high reactivity of irreversible inhibitors means they can be hydrolysed and so destroyed by nucleophiles such as GSH. True or false?

A

True

34
Q

The high reactivity or irreversible inhibitors means that they are likely to be destroyed by attacking other cellular components e.g. DNA True or false?

A

True - can lead to mutation or cancer

35
Q

What are the pharmaceutical drawbacks or irreversible inhibitors?

A

Their chemical reactivity - leads to them being prone to destruction
Their lifetimes are limited by the rate of protein turnover for the target enzyme

36
Q

What are the advantages of mechanism based inhibitors?

A

Absolute specificity

High enzyme inhibition efficiency - tight covalent bonds

37
Q

Increasing the concentration of substrate has no effect on suicide inhibitors. True or false?

A

True - non-competitive irreversible inhibitors

38
Q

What is an example of a suicide inhibitor?

A

5-fluorouracil

39
Q

What are the pharmaceutical drawbacks of suicide inhibitors?

A

The inhibitor structure may still bind to other cell components
There is a problem if the target enzyme is synthesised in the cell as an active precursor
Can cause toxicity due to their high reactivity

40
Q

Penicillin acts on enzymes via a suicide inhibitor mechanism. True or false?

A

True

41
Q

What drug is a irreversible inhibitor of B-lactamase?

A

Clavulanic acid

42
Q

Clavulanic acid has good antibacterial activity. True or false?

A

False

43
Q

Clavulanic acid is used as a guard drug for _______

A

ampicillin

44
Q

The more stable the transition state, the easier the reaction will be and the more effective the enzyme will be as a catalyst. True or false?

A

True

45
Q

Transition state inhibitors bind less tightly than drugs that mimic the substrate or product. True or false?

A

False - bind more tightly

46
Q

Renin inhibitors are examples of ______ _______ inhibitors

A

transition state

47
Q

Transition state inhibitors are designed to mimic the transition state of an enzyme-catalysed reaction. True or false?

A

True

48
Q

Transition state inhibitors are chemically stable. True or false?

A

True

The Medicine (Y2) (34 decks)

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