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MCBG > Regulation of Protein Function > Flashcards

Regulation of Protein Function Flashcards

1
Q

How are enzymes regulated in the short term?

A

Substrate and product concentration

Change in enzyme conformation- allosteric regulation, covalent modification or proteolytic cleavage

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2
Q

How are enzymes regulated in the long term?

A

Change in rate of protein synthesis

or change in rate of protein degradation

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3
Q

What is an Isoenzyme?

A

Different forms of the same enzyme that have different kinetic properties

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4
Q

What is product inhibition?

A

Accumulation of the product of a reaction inhibits the forward reaction

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5
Q

What are allosteric enzymes?

A

Show a sigmoidal relationship between rate and substrate concentration

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6
Q

Why do allosteric enzymes have a sigmoidal shape?

A

Multi subunit so have two different conformations
T state- low affinity
R state- high affinity

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7
Q

What are allosteric activators?

A

Increase proportion of enzyme in the R state

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8
Q

What are allosteric inhibitors?

A

Increase the proportion of enzyme in the T state

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9
Q

What does phosphofructokinase do?

A

allosterically regulated and sets pace of glycolysis

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10
Q

What does Protein kInases do?

A

Transfer the terminal phosphate from ATP to the OH group of Ser, Thr or Tyr

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11
Q

What do Protein phosphatases do?

A

Reverse the effects of kinases by catalysing the hydrolytic removal of phosphoryl groups from proteins

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12
Q

Why are Protein phosphatates so effective?

A

Adds 2 negative charges
Phosphor group can make H bonds
Rate of phosphorylation/ dephosphorylation on can be adjusted
amplification effects
Links energy status of cell to metabolism through ATP

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13
Q

What is amplification by enzyme cascades?

A

When an enzyme activated enzymes the number of affected molecules increased geometrically

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14
Q

What are Zymogens?

A

inactive precursors

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15
Q

What is an Endogenous inhibitor

A

binds to protein and stops activity

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16
Q

How does a chain in rate of protein synthesis occur?

A

Enzyme induction or repression

17
Q

How does a change in rate of protein degradation occur?

A

Ubiquitin-proteasome pathway

18
Q

What is the intrinsic pathway of the blood clotting cascade?

A

Damaged endothelial lining of the blood cells promote binding of fact XII

19
Q

What is the extrinsic pathway of the blood clotting cascade?

A

Trauma released tissue factor III

20
Q

Why is factor X important?

A

Common end point for both pathways

causes thrombin activation

21
Q

What does Thrombin activation cause?

A

Formation of Fibrin clot

22
Q

What is the molecular prothrombin?

A

Protease function is contained in the C-terminus domain
Two kringle domains keep prothrombin in the inactive form
Gla domains target it to appropriate sites for activation

23
Q

What is the role of Gla residues?

A

Allows integration with sites of damage and brings together clotting factors

24
Q

What is calciums role with prothrombin?

A

Calcium binds at Gla residues so only prothrombin next to site of damage will be activated- localised

25
Q

What is the structure of Fibrinogen?

A

2 sets of tripeptides with alpha, gamma and beta joined at the N terminus by disulphide bonds
3 globular domains linked by rods
alpha and beta- negative at n terminus to prevent aggregation

26
Q

How is a fibrin clot formed?

A
  1. Thrombin cleaves fibrinopeptides A and B from the central globular domain of fibrinogen
  2. Globular remains at the end of the C terminus ends of the B and G chains interact with exposed sequences at the N terminus of the cleaves A and B chains to from fibrin mesh
  3. amide bonds form between side chains of Lysine and Glutamine
  4. Transglutaminase catalyses the cross linking which is activated by protransgultaminase by Thrombin
27
Q

What causes Haemophilia?

A

defect in factor VIII

Accelerated clot formation

28
Q

How is the clotting process stopped?

A
  1. Localisation of prothrombin- dilute clotting factors by blood flow and removal by liver
  2. digestion by proteases
  3. specific inhibitors e.g. AT3
29
Q

What is Fibrinolysis?

A

The enzymatic breakdown of the fibrin in blood clots

30
Q

What are the key control points in blood clotting?

A
  1. Inactive zymogens at low concentration
  2. proteolytic activation
  3. amplification by cascade mechanism
  4. Clustering of clotting factors a site of damage
  5. feedback activation by thrombin- continuation of clotting
  6. termination by multiple mechanisms
  7. Clot breakdown controlled by proteolytic activation
31
Q

What forms a clot?

A

Aggregation of Fibrin

32
Q

What does plasmin do?

A

proteolytic cleavage of Fibrin- reverses clot formation

MCBG (19 decks)

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