Enzyme Inhibition and Regulation L3

Question 1

What is the basic premise on which enzyme inhibition is able to occur?

Answer 1

• Able to affect specific enzymes
• Sulfadrugs = inhibitors of folic acid synthesis mainly affecting bacteria
• Methotrexate = inhibits dNTP production and hence DNA synthesis of malignant cells
• Aspirin = inhibits prosta-gland synthesis, responsible mainly for arthritis

Question 2

What are the two main broad groupings of enzyme?

Answer 2

Irreversible- covalent modification of the enzyme structure

Question 3

Explain how Km and Vmax are affected for a competitive enzyme:

Answer 3

Vmax- same

Km- higher

Question 4

Explain how Km and Vmax will be affected for non-competitive enzyme:

Answer 4

Km- the same

Vmax- lower

Question 5

Explain how Km and Vmax will be affected for a uncompetitive enzyme:

Answer 5

Km- lower

Vmax- lower

Question 6

Explain the properties of an allosteric enzyme:

Answer 6

• Activity is controlled by effector molecules binding at distinct allosteric sites
• Binding causes conformational change
• Binding of first substrate induces high affinity substrate in the bound state as well as in many other contacting subunits, the other subunits will now bind with high affinity

Question 7

Explain the properties of covalent modification:

Answer 7

• reversible + rapid reactions

- e.g. phosphate, methyl, acetyl

Question 8

Explain what is meant by the term proteolytic activation:

Answer 8

Very quick. Stored for a long time as zymogen then it is cleaved to produce the irreversible enzyme.

Question 9

Explain what is meant by rate of enzyme synthesis/degradation:

Answer 9

Velocity of reaction dependant on [enzyme], this can be controlled by the rate at which it is synthesised or degraded.

Question 10

Explain what is meant by compartmentalisation:

Answer 10

Anabolic and catabolic reactions are separated into different compartments within the cell.

Question 11

Explain what is meant by the term regulation by control proteins:

Answer 11

• Calmodulin = calcium - modulating protein
• Mediates many calcium driven metabolic reactions
• 4 binding sites for Ca2+
• When the calcium concentration rises it then binds to the protein
• Calmodulin is then activated and regulates other proteins