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Biochemistry > Enzyme catalytic strategies > Flashcards

Enzyme catalytic strategies Flashcards

1
Q

2 things that enzyme activity depend on?

A

pH
Temperature

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2
Q

How does increase in temp affect enzyme activity?

A

Increases it as molecules move faster

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3
Q

4 catalytic principles used by enzymes

A

Covalent catalysis
General acid-base catalysis
Catalysis by approximation
Metal ion catalysis

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4
Q

Which catalytic strategies does chymotrypsin combine?

A

Covalent, acid-base and transition-state

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5
Q

What does protease catalyse?

A

Proteolysis
Cuts down proteins

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6
Q

Difference between nucleophile and electrophile

A

Nucleophile: Accepts protons and donates electrons
Electrophile: Donates protons and accept electrons

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7
Q

What is chymotrypsin involved in?

A

Breaking down proteins into small peptides by cutting a specific location on peptide backbone

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8
Q

What is the catalytic triad?

A

Serine, Histadine and Asperegine
They have to be close in the folding

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9
Q

Where does the cutting occur in chymotrypsin?

A

In the hydrophobic pocket, the serine cuts the protein when it is attached to the hydrophobic pocket

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10
Q

What does the oxyanion hole do?

A

Protects the enzyme

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11
Q

Does the S1/hydrophobic pocket differ in protease?

A

Yes

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12
Q

Do proteases cut in only one point?

A

Yes

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13
Q

What allows for the specificity in proteases?

A

The difference in hydrophobic pockets

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14
Q

Example of aspartyl protease

A

Pepsine

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15
Q

What is site-directed mutagenesis?

A

Replace one amino acid with another
Example how the catalytic triad was discovered

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16
Q

3 classes of proteases

A

Cysteine
Aspartyl
Metalloproteases

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17
Q

Which amino acid is conservative replacement (keep good activity) in serine?

A

Cystine

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18
Q

What is indinavir?

A

Analogue of the substrate

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19
Q

What does carbonic anhydrase do?

A

Make a fast reaction faster
Helps with metabolism

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20
Q

How many carbonic anhydrasases (esoenzymes) in the body?

A

7

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21
Q

What is the Kcat?

A

Enzyme turn-over number
Amount of product produced per unit of time per enzyme

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22
Q

How does pH effect carbonic anhydrase activity?

A

Reaction is higher (Kcat) in basic environment because a group that loses a proton plays an important role in the activity of carbonic anhydrase

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23
Q

Which was the first enzyme that uses a metal that was discovered?

A

Carbonic anhydrase

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24
Q

What is lysozyme?

A

An antibacterial enzyme

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25
Q

What does lysozyme attack?

A

Peptidoglycan

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26
Q

What is peptidoglycan?

A

Polysaccharide found in many bacterial cell walls

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27
Q

Example of where lysozyme I found?

A

In the numerous body fluid (blood, sweat, saliva, sweat, tears, urine)

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28
Q

What are isoenzymes?

A

Enzyme variants that are the product of different genes and thus represent

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29
Q

What are allozymes?

A

different loci
Enzymes that are the product of different alleles of the same gene

30
Q

Why are isoenzymes clinically relevant?

A

Helps determine where the enzymes in the tissue are coming from. This helps determine if there are for example liver damage (if there are liver enzymes present in the blood)

31
Q

How can heart attacks be found out with the help of isoenzymes?

A

If heart enzymes are found in the blood when isoenzymes are separated by electrophoresis there can be a sign of heart attack

32
Q

How are different isoenzymes identified?

A

Electrophoresis (because of charge and size)

33
Q

What is the same in isoenzymes?

A

The active site

34
Q

What kind of enzyme class do proteases belong to?

A

Hydrolase

35
Q

Can a nonbiological catalyst produce more than one product with the occurrence of side reactions?

A

Yes

36
Q

Must a substrate bind to the active site before catalysis can occur?

A

Yes

37
Q

Do enzymes change the free energy of a reaction?

A

No

38
Q

What is the optimal temperature for enzyme activity?

A

35-45c

39
Q

Is the optimal pH the same for all enzymes?

A

No it very much depends on the enzyme and its function and where its found

40
Q

What is covalent catalysis?

A

Active site contains a nucleophile that is briefly covalently modified

41
Q

What is general acid-base catalysis?

A

A molecule other than water donates or accepts a proton

42
Q

What is catalysis by approximation?

A

A molecule other than water donates or accepts a proton

43
Q

What is metal ion catalysis?

A

Can function in different ways
Example: electrophilic catalyst

44
Q

What does the hydrophobic pocket recognise?

A

Peptide bonds

45
Q

Why does apartyl protease work best in acidic conditions?

A

Because it can be protenated

46
Q

Serine, histamine and superfine in the catalytic triad are not close when looking at the primary structure, how do they make up the catlytic triad?

A

They are close in the tertiary structure thanks to the folding

47
Q

What in chymotrypsin catalyses the cleavage of peptide bonds ?

A

The catalytic triad

48
Q

What explains substrate specificity of trypsin, chymotrypsin and elastase?

A

Structual difference in the binding site

49
Q

What is the rocket in chymotrypsin, polar or nonpolar?

A

Nonpolar

50
Q

How does the pocket of trypsin differ from that of chymotrypsin?

A

It has Asp instead of Ser

51
Q

How does elastase differ from chymotrypsin?

A

There are no pockets present

52
Q

Why are there no pockets in elastase?

A

Because 2 glycerine is replaced by Val and Thr

53
Q

What does the hydrophobic pocket of chymotrypsin bind?

A

Aromatic amino acids

54
Q

Is chymotrypsin hydrophobic or hydrophilic?

A

Hydrophobic

55
Q

Why does the group have to be protected to work better in aspartyl proteases?

A

Because the conditions have to be acidic

56
Q

What is pepsin?

A

An aspartyl protease

57
Q

How do metalloproteases work?

A

The peptide carbonyl group is attacked by a metal-activated water molecule

58
Q

What carbonic anhydrase used to do in animals?

A

Transport CO2 out of muscles and maintain blood pH balance

59
Q

What catalyses the reaction of hydration CO2 to form bicarbonate?

A

Carbonic anhydrase

60
Q

Which ion is found at the active site of carbonic anhydrase?

A

Zinc ion

61
Q

What does catalysis with carbonic anhydrase entail?

A

Zinc activation of a water molecule

62
Q

What does zinc ion promote the ionisation of? and what does it result in

A

Bound H2O, resulting nucleophilic OH- attacks carbon of CO2

63
Q

Why does the zinc in carbonic anhydrase make the reaction much faster?

A

Because water without zinc is a very weak acid/nucleophile

64
Q

What is peptidoglycan?

A

A polysaccharide found in many bacterial cell walls

65
Q

What does the cleavage of the cell wall of bacteria lead to?

A

Lysis of bacteria

66
Q

Antibacterial enzyme

A

Lysozyme

67
Q

When is lysozyme released into the blood stream?

A

When granulocytes and monocytes are released

68
Q

What does lactate dehydrogenase catalyse?

A

A step in anaerobic glucose metabolism and glucose synthesis

69
Q

What does LDH stand for?

A

Lactate dehydrogenase

70
Q

Why can isozymes be exerted by electrophoresis?

A

Because they differ slightly in charge

Biochemistry (28 decks)

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