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Molecules to Cells - Biochemistry > Lecture 10. Enzymology 2 > Flashcards

Lecture 10. Enzymology 2 Flashcards

1
Q

What does the drug methotrexate (trexall) do and what enzyme does it inhibit ?

A
  1. Oncology and inflammatory disease
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2
Q

What does the drug astoravatin (lipitor) do and what enzyme does it inhibit ?

A
  1. Reduces cholesterol levels

2. HMG-CoA reductase

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3
Q

What is a lipitor ?

A

A statin which inhibits synthesis of cholestrol

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4
Q

In competitive inhibition, what is the Vmax ?

A

The Vmax is unchanged because inhibition can be overcome by a sufficiently high concentration of substrate

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5
Q

What is mixed inhibition (non-competitive) ?

A

The inhibitor binds to both the enzyme or enzyme substrate complex

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6
Q

What is an uncompetitive inhibition ?

A

The inhibitor binds only to the enzyme substrate complex in what is essentially substrate dependent inhibition

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7
Q

What is a competitive inhibitor ?

A

The inhibitor is structurally similar to the substrate and can bind to the active site, preventing the actual substance from binding

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8
Q

Are humans effected by sulfanilamide ?

A

No, because humans get folic acid in their diet

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9
Q

What is the function of sulfanilamide ?

A

Mimics p-aminobenzoic acid (PABA), which is a metabolite needed by bacteria for synthesis of the coenzyme folic acid. It binds to the enzyme that normally metabolises PABA and competitively inhibits it, preventing folic acid synthesis

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10
Q

What does the drug oceltamivir (tamiflu) do and what enzyme does it inhibit ?

A
  1. Influenza

2. Viral neuraminidase

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11
Q

What does the drug lmatinib (gleevec) do and what enzyme does it inhibit ?

A
  1. Oncology

2. BCR-ABL Kinase

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12
Q

What does the drug siloenofil (viagra) do and what enzyme does it inhibit ?

A
  1. Pulmonary artery hypertension and erectile dysfunction

2. Type 5 phosphodiecterase

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13
Q

What does the drug fluoxetire (prozac) do and what enzyme does it inhibit ?

A
  1. Antidepressant

2. Pre-synaptic seretonin receptors

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14
Q

What stabilises the tetrahedral reaction intermediate ?

A

Oxyanion hole (region in the active site)

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15
Q

What does asparate do to serine 195 ?

A

Orients the histidine and renders it a better proton acceptor

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16
Q

What does the alkoxide ion do to the substrate ?

A

Attacks the peptide bond

17
Q

What is histidine’s role in serine 195 ?

A

Histidine acts as a base catalyst, removing a proton from serine 195 and generating a highly reactive alkoxide ion

18
Q

What is serine part of ? Name the other members of the group.

A

A catalytic triad. With histidine and aspartate

19
Q

What is the only group specific reagent that only modifies serine 195 ?

A

Disopropylphosphofluoridate

20
Q

What happens to serine 195 during catalysis ?

A

It becomes a strong nucleophile that attacks the carbonyl group of the peptide bond in the substrate

21
Q

What is the function of chymotrypsin ?

A

Hydrolyzes peptide bonds selectively on the carboxyl side of the large hydrophobic residues

22
Q

Where is chymotrypsin secreted from ?

A

The pancreas

23
Q

What type of enzyme is chymotrypsin ?

A

A proteolytic enzyme

24
Q

Is protein hydrolysis exergonic or endergonic

A

Exergonic but kinetically very slow

25
Q

What makes peptide (protease) resistant to hydrolysis ?

A

The resonance structure of the peptide bond

26
Q

What is metal ion catalysis ?

A

Many functions eg. electrophilic catalyst

27
Q

What is catalysis by proximity ?

A

The enzyme brings two substrates together in an orientation that facilitates catalysis

28
Q

What is general acid base catalysis ?

A

A molecule other than water donates or accepts a proton

29
Q

What is covalent catalysis ?

A

The active site contains a nucleophile that is briefly covalently modified

30
Q

What are double displacement reactions ?

A

Characterised by the formation of a substituted enzyme intermediate

31
Q

What are sequential reactions ?

A

May be random or ordered. They can be characterized by the formation of a ternary complex consisting of the enzyme and both substrates

Molecules to Cells - Biochemistry (17 decks)

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