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BS129: Physiology, Neurobiology and Metabolism > Lecture 3. Effects of pH and T on Enzyme Activity and Enzyme Inhibitors and Inhibition > Flashcards

Lecture 3. Effects of pH and T on Enzyme Activity and Enzyme Inhibitors and Inhibition Flashcards

1
Q

What are the axes for an Eadie-Hofstee plot?

A

x axis = v/[S]
y axis = v

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2
Q

On an Eadie-Hofstee plot, what does the y-intercept represent?

A

Vmax

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3
Q

On an Eadie-Hofstee plot, what does the x-intercept represent?

A

Vmax/Km

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4
Q

On an Eadie-Hofstee plot, what does the gradient represent?

A

-Km

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5
Q

When temperature increases, what happens to the rates of enzyme-catalysed reactions?

A

The rates of enzyme-catalysed reactions increase

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6
Q

What is Q10 generally for biological reactions?

A

2 - the rate doubles for every 10 degree rise in temperature

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7
Q

What enzymes do not denature at high temperatures?

A

Enzymes derived from organisms living in hot environments and enzymes from thermophiles

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8
Q

What enzyme is used in PCR?

A

Taq polymerase

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9
Q

What does the pH-dependence of an enzyme’s activity reflect?

A

The ionisation of groups on S and in the active-site of E

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10
Q

What can pH affect?

A

Both Km and kcat

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11
Q

What can pH-dependence provide useful insights into?

A

pH-dependence can provide useful insights into the
nature of groups (amino acid side chains) involved in the
active site

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12
Q

What is ACE?

A

Angiotensin-converting enzyme

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13
Q

What is an example of an ACE inhibitor?

A

Enalapril

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14
Q

What are ACE inhibitors used for?

A

Treatment of hypertension, diabetic nephropathy, and some types of chronic heart failure

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15
Q

How do ACE inhibitors work?

A

ACE inhibitors lower blood pressure by blocking production of a signal promoting blood vessel contraction

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16
Q

How does aspirin work?

A

Aspirin inhibits an enzyme that produces prostaglandin, blocking the inflammatory response

17
Q

How does penicillin work?

A

Penicillin inhibits enzymes which enable bacteria to make stable, robust, cross- linked cell walls. It fixes the enzyme in the ES complex

18
Q

What do many drugs target?

A

Enzymes

19
Q

What is an example of a receptor targeting drug?

A

Beta-blockers

20
Q

How do Beta-blockers work?

A

Beta-blockers bind and inhibit the action of noradrenaline on β-adrenergic receptors

21
Q

How does irreversible enzyme inhibition occur?

A

When an inhibitor reacts covalently with essential active sites

22
Q

What are examples of irreversible inhibitors?

A

Organomercurials and nerve gas

23
Q

What do organomercurials target?

A

Cys residues

24
Q

What does nerve gas target?

A

Reactive Ser residues

25
Q

What does mercury inhibit?

A

Selenoenzymes

26
Q

How does iodoacetamide inactivate enzymes?

A

Iodoacetamide inactivates enzymes by reacting with critical cysteine residues

27
Q

How does DIPF inactivate enzymes?

A

DIPF is a nerve gas; it inactivates acetylcholinesterase by reacting with a highly reactive serine in the active site

28
Q

What are two types of reversible inhibitors?

A

Competitive and non-competitive

29
Q

How do competitive inhibitors function?

A

Competitive inhibitors act by blocking substrate binding
(they compete with S to bind to E) and are often
structural homologues of S

30
Q

How do non-competitive inhibitors function?

A

Non-competitive inhibitors bind at same time as S, but
not in the same site, and act by slowing down
conversion to P

31
Q

What does competitive inhibition imply at very high [S]?

A

S will displace I; therefore, even in the presence of I E will become saturated with S

32
Q

What is oseltamivir?

A

A competitive inhibitor of neuraminidase. It mimics a natural substrate acetyl sialic acid

33
Q

What are the effects of a competitive inhibitor on Vmax and Km?

A

A competitive inhibitor has no effect on V max but increases Km

34
Q

What are the effects of a non-competitive inhibitor on Vmax and Km?

A

A non-competitive inhibitor decreases Vmax but has no effect on Km

35
Q

What graph would you plot to distinguish competitive from non-competitive inhibitors?

A

Lineweaver-Burk plot

BS129: Physiology, Neurobiology and Metabolism (34 decks)

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