Enzymes

Question 1

What are the relevance of enzymes to medicine?

Answer 1

• Defects in enzymes underlie many diseases
• 30-40% of drug targets are enzymes
• Enzymes can be drugs themselves
• Enzyme activity can be diagnostic/prognostic
• Enzymes are tools in diagnostic/ prognostic tests

Question 2

What are enzymes?

Answer 2

Enzymes are biological catalysts of chemical reactions and nearly all are proteins.

Question 3

What are the functions of enzymes?

Answer 3

• Specific action on particular biochemical compounds (substrates)
• Increases the rate at which the reaction equilibrium is reached, but do NOT shift the position of equilibrium

Question 4

What is a sign that equilibrium has been reached?

Answer 4

If the forward and backward reaction rates are equal

Question 5

What is the equation for equilibrium constant?

Answer 5

K= [products]/ [reactants]

Question 6

How do enzymes decrease the activation energy of a reaction?

Answer 6

• By providing catalytically competent groups for a specific reaction mechanism
• By binding substrates such that their orientation is optimised for the reaction
• By preferentially binding and stabilising the transition states of the reaction

Question 7

What is the active site of an enzyme?

Answer 7

This is a region of the enzyme at which substrate binding and conversion to product takes place

• 3D space comprising of the protein structure
• may represent only a small part of the protein structure
• binds substrate via multiple weak interactions
• provides substrate specificity because of its unique 3D arrangement of atoms

Question 8

Give an example of an enzyme active site

Answer 8

Trypsin

• proteolytic digestive enzyme
• Three key amino acids in active site, but far apart in amino acid sequence
• Active site is niche for binding substance

Question 9

What is the test measuring enzyme activity

Answer 9

Enzyme Assay

Question 10

What does the Michaelis- Menten constant tell us?

Answer 10

• Michaelis-Menten model is used to describe the chemical processes that lead from the transition of a substrate to a product in an enzyme-catalysed reaction:

Question 11

What do each of the values stand for in the Michaelis- Menten constant?

Answer 11

k1= the rate of formation of the enzyme-substrate complex

K2 and k3 are the rates of dissociation of ES complex