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Enzymes Flashcards

1
Q

By what factorcan enzymes accelerate chemical reactions?

A

10^5- 10^19

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2
Q

What enzyme accelerates reactions the most?

A

Arginine decarboxylase (10^19)

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3
Q

What can enzymes be affected by?

A

Inhibitors and activators

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4
Q

What is a holo enzyme?

A

Enzyme containing non-protein cofactor

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5
Q

What is an apoenzyme?

A

Enzyme that doesn’t contain a non-protein cofactor

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6
Q

What does the group EC1 Oxidoreductases do?

A

Catalyze redox reactions
NADPH oxidation to NADP+ ,molecule reduction

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7
Q

What does the group EC2 Transferases do?

A

Transfer the functional group
tRNA AA is transferred to the created protein

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8
Q

What does the group EC3 Hydrolases do?

A

Hydrolyze bonds
Digestive enzymes split bonds

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9
Q

What does the group EC4 Lyases do?

A

Non-hydrolytic bond cleavage

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10
Q

What does the group EC5 Isomerases do?

A

Molecular isomerization
Isomer is rearranged spatially (molecular weight stays the same)

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11
Q

What does the group EC6 Ligases do?

A

Join 2 molecules covalently

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12
Q

What does the group EC7 Translocases do?

A

Move the molecule around the cell

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13
Q

Name the 4 enzyme regulation processes

A
  1. Bioavailability
  2. Covalent modification
  3. Allosteric regulation
  4. Compartmentation
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14
Q

What does bioavailability do?

A

Cell controls how much of the synthesized enzyme will be used /available by the substrate
Degrades it if too much
Binds to regulatory molecule
Coucuent modification

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15
Q

What is repression in bioavailability

A

Product of a biochemical pathway inhibits synthesis of a key enzyme in the pathway
Feedback inhibition

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16
Q

What is induction in bioavailability?

A

Coulchanges the production of a specific enzyme to stimulate / inhibit activity

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17
Q

What is the issue with bioavailability?

A

It is too slow to control all cell functions

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18
Q

What is covalent modification?

A

Covalently attaching a moleculeto the enzyme to stimulate / inhibit activity
Much faster than genetic control
Uses (de)phosphorylation

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19
Q

What catalyzes phosphorylation?

A

Catalyzed by enzymes kinases
ATP isthe source ofthe phosphate

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20
Q

What catalyzes dephosphorylation?

A

Catalyzed by phosphatase enzymes

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21
Q

What other molecules covalently modify enzymes?

A

Methyl/acetyl groups, sugars, lipids
Less commonly Than phosphate

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22
Q

What are the sites for phosphorylation?

A

The OH side chain of serinine, threonine, tyrosine

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23
Q

What is an example of covalent modification?

A

Proteolytic processing to activate and deactivate enzymes

24
Q

What is allosteric inhibition?

A

Feedback inhibition
Catalyzes the committed step in a metabolic pathway- controls the vote
Doesn’t always follow the Michaelis-Menten kinetics

25
What is an exampleof allosteric regulation?
Phospho-fructokinase (step 3 of glycolysis) ATP is a negative regulator
26
What is compartmentation?
Storing enzymes in specific compartments Keep them from doing damage or provide proper conditions for activity
27
Describe the lock and key model
Enzyme and substrate possesses specific complementary shapes that fit exactly into eachother Doesn't explain the transition state that ES complex achieve - proven inaccurate model
28
Describe the induced fit model
Enzyme slightly changes shape upon substrate binding Active site forms a complementary shape after substrate binds
29
Describe the substrate in a transition state
Short-lived, unstable, requires less activation energy
30
Describe conformational selection
Newer model of the induced fit model Enzyme adapts to substrate dependent on the environment and presence of regulatory molecules
31
How enzymes affect the activation energy?
Lower the activation energy of a chemical reaction by the randomness of collisions between molecules Help bring the substrates together in proper orientation so that the reaction can occur
32
What information enzyme kinetics give?
About enzyme catalysis, mechanism, activity regulation, basis of enzyme assays
33
What are enzyme kinetics affected by?
By enzyme, substrate, ph, temperature, co-enzymes, activators, inhibitors
34
What is a steady state?
When ES builds up initially and then remain constant Will persist until thesubstrate runs out takes nearly all of the reaction time
35
Describe 1st order reaction
The reaction rate is proportional to the substrate There is move enzymethan substrate
36
Describe 2nd order reaction
More substrate than enzyme Substrate is not proportional to the reaction rate Rate depends only on the enzyme
37
Describe michaelis-menten kinetics.
Under physiological conditions enzymes are not saturated with substrates Reaction rate is dependent on substrate concentration
38
What does the Michaelis constant describe
The affinity of an enzyme for a substrate Lower Km = higher affinity
39
What is the turnover number?
K cat Number of substrate molecules cleaved per enzyme molecules per time when enzyme is fully saturated
40
What plots describe the Michaelis-menten kinetics
Lineweaver- Burk plot Hanes-woolf plot Eddie- hofsteeplot
41
What are inhibitors?
Interact with enzymes to reduce their catalytic activity Structurally similar to natural substrate of an enzyme
42
Features of reversible inhibition
Reversibly bind and dissociate from enzyme Activity of enzyme recovers when inhibitor is diluted out Non covalent interactions
43
Name reversible inhibition types:
Competitive inhibition Non-competitive inhibition Uncompetitive inhibition
44
Features of irreversible inhibition
Inactivators that irreversibly associate with an enzyme Activity of enzyme doesn't recover with dilution Covalent interactions
45
Describe competitive inhibition:
Direct competition between I and S for binding I binds to active site of S I only bina to free enzymes Most common type of inhibition
46
What are examples of competitive inhibition
HIV protease inhibitor Phosphodiester-5 inhibitor
47
Describe the kinetics of competitive inhibition
Vmax is unchanged Km increases as higher S concentration is needed to reach max Low Ki = higher affinity Less affinity for S occurs
48
Feature of uncompetitive inhibition
Inhibitor binds to ES complex (not free E) Binds to allosteric site Common in multi-substrate reactions
49
Example of uncompetitive inhibition
Lansoprazole for gastric reflux
50
Kinetics of uncompetitive inhibition
Km is lower Vmax is lower
51
Features of non-competitive inhibition
Inhibitor binds to both free enzymes and ES complex Binds to allosteric site ESI complex doesn't react
52
Example of non-competitive inhibition
Nifedipine inhibits CYP29 (cytP450 enzyme involved in drug metabolism)
53
Kinetics of non-competitive inhibition
Km is unchanged Vmax is lowered At high S, the inhibitor is still bound to the enzyme
54
Detailed Features of irreversible inhibition
Enzyme inactivated or suicide inhibition Inhibitors form covalent bonds with their target enzymes leading to permanent inactivation Used to identify the functional AA within the active site
55
Describe the irreversible inhibition on aspirin
Aspirin covalently modifies the enzyme prostaglandin H synthase Prevents prostaglandin synthesis and lowers inflammation Occurs vidacetylation of serine-530 at the active site of PGH synthesis
56
Describe the irreversible inhibition on eflornithine
Is a suicide inhibitor treating sleeping sickness Binds irreversibly to cysteine residue on ornithine decarboxylase Reduces production of polyamides necessary for parasite growth
57
Describe the irreversible inhibition on penicillin
Is a irreversible inhibitor of bacterial wall synthesis Innibits peptidoglycan cell wall synthesis and makes bacteria susceptible to osmosis Without thePG layer bacteria lyse Penicillin covalently modifies glycopeptide transpeptidase

Biomolecules And Metabolism (7 decks)

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