MB - Metabolic Control via Enzyme Regulation I Flashcards

1
Q

What is a metabolic pathway?

A

The enzymatic route that a metabolite molecule takes

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2
Q

What are the rate-limiting steps of a metabolic pathway?

A
  1. Slowest reaction in the pathway
  2. Usually the first unique enzyme in a pathway
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3
Q

What are 3 ways to identify the RLS?

A

1) Measure Vmax for enzymes in a pathway
* Lowest- RLS

2) Compare Keq and mass action ratios
* MAR is usually 100-1000 times < Keq for RLS

3) Test if step is at crossover point

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4
Q

What 2 enzymes are of regulatory importance in glycolysis?

A
  1. Hexokinase
  2. Phosphofructokinase-1
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5
Q

What is the need for metabolic control? (3)

A
  • Ensures a given metabolic pathway is active when its product is needed
  • Ensures competing pathways aren’t simultaneously active
  • Ensures co-ordinated activity in multiple related pathways
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6
Q

What are the 3 types of enzyme regulation?

A

1) Intrinsic control by metabolites- Allosterism/Inhibitors

2) Fast extrinsic control via hormones- Covalent modification (phosphorylation)

3) Slow extrinsic control via hormones- Gene expression

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7
Q

What is product inhibition?

A

The product acts to inhibit the enzyme making it
* e.g G-6-P inhibits its own production in glycolysis (Hexokinase)

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8
Q

What is allosterism?

A

The interaction between molecules influences the binding of another
* e.g F-2,6-P2 increases PFK-1 activity
* e.g F-2,6-P2 inhibits FBPase-1 activity

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9
Q

What do hormones alter in relation to enzymes?

A

Activity of enzymes
* Rapid, via phosphorylation
* Short-lived effect

Number of enzymes
* Slow, via gene expression changes
* Longer-lived effect

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10
Q

How does phosphorylation alter the activity of enzymes?

A

Phosphorylation –> Conformational change
–> Activation or Inactivation

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