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BIOS4007 - Enzyme Kinetics > Enzyme Regulation > Flashcards

Enzyme Regulation Flashcards

1
Q

What are cofactors?

A

Addition of another non-protein molecule for enzyme activity.
- organic/inorganic

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2
Q

Two types of cofactors?

A
  • essential ions
  • coenzymes
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3
Q

What are the two classes of essential ions as cofactors?

A
  • activator ions
  • metal ions of metallo-enzymes
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4
Q

What are activator ions?

A

Metal or non-metal ions that
- bind to enzymes
- increase their activity

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5
Q

What are metallo-enzymes?

A

Enzymes that require a metal ion as a cofactor to catalyze a biochemical reaction.

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6
Q

How do activator ions function as cofactors?

A

Works by:
- stabilizing the E-S complex
- enhancing the binding of substrate molecules
- inducing a conformational change in the enzyme that makes it more catalytically active

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7
Q

How do metal ions of metallo-enzymes function as cofactors?

A

Participate directly in catalysis by serving as the active site

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8
Q

How do metal activated enzymes function as cofactors?

A
  • stimulated by addition of metal ions
    e.g. Mg2+
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9
Q

What is Mg2+ used in as a cofactor?

A

Glycolysis
- in 1st step of converting glucose to glucose 6-phosphate

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10
Q

What are the two classes of coenzymes as cofactors?

A
  • co-substrates
  • prosthetic groups
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11
Q

What are co-substrates?

A

Small molecules that participate in a biochemical reaction as a reactant but are not consumed in the reaction.

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12
Q

What are prosthetic groups?

A

Non-protein molecules that are tightly bound to enzymes and help them catalyze a reaction.

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13
Q

How do co-substrates function as coenzymes?

A
  • altered in reaction
  • regenerate to original structure in next reaction
  • disassociated from active site
  • shuttle chemical groups among different enzyme reactions
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14
Q

How do prosthetic groups function as coenzymes?

A
  • directly participates in catalytic activity
  • provides specific shape to enzyme’s AS
  • stabilise intermediates or transition states
  • facilitate electron transfer
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15
Q

What do co-substrates and prosthetic groups supply to amino acid side chains?

A

Reactive groups not present on amino acid side chains.

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16
Q

Summarise the classes of cofactors in a diagram

A

silde 11

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17
Q

What is the main clinical symptom caused by the malfunction of enzymes?

A

Dietary vitamin insufficiency

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18
Q

What does dietary vitamin insufficiency lead to?

A

Lack of sufficient cofactors derived from vitamins to maintain homeostasis.

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19
Q

Why does enzyme activity have to be regulated?

A
  • prevent the stability of cells with their surroundings (maintain homeostasis)
  • allow cellular events to be optimised according to need (to respond to changing conditions)
  • increase/decrease the amount of enzyme (to ensure the appropriate level of enzyme activity)
  • alter the catalytic properties of an existing enzyme (to prevent wasteful reactions)
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20
Q

Effect of temperature on catalysis

A
  • increasing temp increases rate of reaction
  • increases V0
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21
Q

What is denaturation?

A
  • complete loss of catalytic activity
  • due to protein unfolding (loses its 3-D structure)
  • caused by change in environment (e.g. temp, pH)
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22
Q

What is conformal change?

A
  • change in the 3D shape of an enzyme
  • due to binding of a substrate or other ligand
  • has different ΔG values
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23
Q

Effects of pH on catalysis

A

Enzymes have an optimal pH range for maximum activity:
- pH deviates too much from optimal range, E = denatured

Changes in pH leads to:
- charges on amino acid residues in AS also changing
- competitive inhibitors binding to AS
- covalent modifications of E

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24
Q

How does pH have an effect on substrates?

A

Affects:
- ionisation state → affects ability to bind to active site
- solubility of the S → impacts its availability to the enzyme
- stability of S → leads to degradation of S or formation of unwanted side Ps

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25
Q

What is the ionization state of an amino acid side chain?

A

Refers to whether the side chain is charged or uncharged

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26
Q

What happens when there are changes in the ionisation state of an amino acid side chain?

A
  • alters Vmax if the side chain is involved in the catalytic mechanism
  • affects protein (E) structure & function
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27
Q

How does the ionization state of an amino acid side chain affect protein function?

A

Changes in the ionization state of amino acid side chain:
- alters the protein’s (E) ability to bind to other molecules
- or catalyze chemical reactions

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28
Q

What are inhibitors?

A
  • molecule that binds to an enzyme
  • interferes with its activity - reduces or eliminates completely
29
Q

What do inhibitors prevent?

A

Prevent
- formation of ES complex
- ES breakdown to E + P

30
Q

Are inhibitors reversible?

A

Reversible or irreversible

31
Q

How do inhibitors bind to enzymes?

A

Covalent bonds (irreversible)

32
Q

How do reversible inhibitors bind to enzymes?

A

Non-covalent interactions

33
Q

How can inhibition be identified?

A

Michaelis-Menten plot

34
Q

What are the three common types of reversible enzyme inhibition?

A
  • competitive
  • non-competitive
  • uncompetitive
35
Q

What is Competitive Inhibition?

A

Molecules similar in structure to substrate competes with the substrate for the active site

36
Q

How does Competitive Inhibition effect Vmax and Km?

A
  • increases Km without effecting Vmax
37
Q

What is Non-Competitive Inhibition?

A

Inhibitor molecule binds to a site on enzyme different from AS

38
Q

How does non-Competitive Inhibition effect Vmax and Km?

A
  • reduces Vmax
  • Km remains same as inhibitor doesn’t affect binding of S to AS
39
Q

How does non-Competitive Inhibition alter enzymes?

A
  • alters conformation of enzyme’s structure
  • reduce the enzyme’s activity
  • or prevent it from functioning altogether
40
Q

Why are non-Competitive Inhibition preferable to competitive inhibitors?

A
  • do not compete with S for binding to AS
  • ∴ less effected by changes in [S]
  • inhibition caused by inhibitor persist at high [S] (not overcome by high [S])
41
Q

What is Uncompetitive Inhibition?

A
  • inhibitor binds to ES complex
  • forming a ternary complex
42
Q

How does uncompetitive Inhibition work?

A
  • binds to the ES complex
  • prevents ES from releasing P & regenerating enzyme
  • removes E from reaction
43
Q

How does uncompetitive Inhibition effect Vmax and Km?

A
  • lowers both Vmax and Km
  • ratio of Km/Vmax remains same
44
Q

How does covalent inhibition function?

A

Reduces concentration of the active enzyme by:
- irreversibly modifying the enzyme’s AS
- hence decreases rate of reaction

45
Q

How does irreversible inhibition work?

A

Binds to enzyme to alter it’s binding site
- prevents S from binding
- removes E from reaction
- & permanent inactivation of E

46
Q

Effect of irreversible inhibition on Km and Vmax?

A
  • lowers both Vmax and Km
  • ratio of Km/Vmax remains same
47
Q

What triggers dysregulation of enzymes?

A
  • pathogenic agents
  • genetic mutations
    leads to diseases
48
Q

What control mechanisms are used for enzyme regulation in the body?

A
  • course control
  • fine control
49
Q

What is course control?

A
  • involves regulating the overall rate of a metabolic pathway or enzyme system
  • through the activation or inhibition of key enzymes
50
Q

What mechanism is used to achieve course control?

A

control of enzyme quantity

51
Q

What factors affect control of enzyme quantity?

A
  • altering rate of E synthesis & degradation
  • induction
  • repression
  • S, metal ion and coenzyme
52
Q

What is Fine Control?

A

Altering the catalytic efficiency of the enzyme
(reversible changes in the enzyme’s conformation)

53
Q

What is catalytic efficiency affected by?

A
  • allosteric regulation
  • feedback inhibition
  • proenzyme (zymogen)
  • covalent modification
  • protein - protein interaction
54
Q

What is Allosteric Regulation?

A

Binding of a molecule at a site other than the catalytic active site.
- reversible
- non-covalent

55
Q

What are Proenzymes?

A

Inactive enzymes that require activation, existing as:
- zymogens
- proproteins

56
Q

What is Covalent Modification?

A

Common regulatory mechanism
- reversible modification of an enzyme

57
Q

What is Tay-Sach’s Disease?

A

Genetic metabolic disorder affecting the NS:
- caused by deficiency of enzyme hexosaminidase A
- results in failure to process lipid (GM2 ganglioside) that accumulates in brain + tissues

58
Q

How does Tay-Sach’s Disease develop?

A

Infants not developing normally
- decreased muscle tone
- increased startle response
progresses to:
- paralysis
- delayed mental + social development
- deafness
- blindness
- seizures
- death

59
Q

What is Chronic Inflammation?

A

Long-term inflammatory response
- occurs when the body’s immune system attempts to eliminate harmful stimuli
- but is unable to do so effectively

60
Q

How does chronic inflammation affect enzyme regulation?

A

Disrupt regulatory mechanisms such as:
- cofactors
- inhibitors
- feedback mechanisms

61
Q

What are NSAIDs?

A

Non-Steroidal Anti-Inflammatory Drugs
- medications commonly used to reduce pain, fever, and inflammation

62
Q

How do NSAIDs work?

A

Inhibiting the activity of cyclooxygenase (COX-2)
- an enzyme involved in production of prostaglandins
- prostaglandins contribute to pain & inflammation

63
Q

What type of inhibitor is NSAIDs?

A

Competitive inhibitor

64
Q

What are the types of NSAIDs?

A
  • aspirin
  • ibuprofen
  • naproxen
  • diclofenac
65
Q

What are the clinical uses of NSAIDS

A

treats:
- analgesia
- inflammation
- antipyresis
- anti-platelet effect
- cancer preventive agents

66
Q

What are the adverse effects of NSAIDS

A
  • gastrointestinal effects
  • disturbance of renal function
  • inhibition of platelet aggregation
  • central symptoms
67
Q

How do enzymes correlate to tissue damage?

A

Elevated enzyme levels indicates tissue damage

68
Q

How are enzymes used in diagnostics?

A

By measuring elevated enzyme levels as they indicate tissue damage

69
Q

How do enzymes indicate damage to a specific tissue?

A

Presence of increased levels of particular enzymes in plasma
E.g. AMS = damage in salivary glands

BIOS4007 - Enzyme Kinetics (2 decks)

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