Cofactors, coenzymes + prosthetic groups (f)

Question 1

What are cofactors?

Answer 1

Non-protein components necessary for the effective functioning of an enzyme. Not used up.

Question 2

How do cofactors work?

Answer 2

• they may transfer atoms from on reaction to another in a multi-step pathway
• may actually form part of the active site

Question 3

Describe inorganic cofactors

Answer 3

• obtained via the diet as minerals such as iron, calcium etc
• e.g. amylase contains a Cl⁻ ion that is necessary for the formation of a correctly shaped active site

Question 4

What are coenzymes?

Answer 4

• organic cofactors

- changed by the reaction - derived from vitamins - a class of organic molecule found in the diet

Question 5

What is a prosthetic group?

Answer 5

• non-protein component of a conjugated protein
• cofactors required by certain enzymes to carry out their catalytic function
• tightly bound and form a permanent feature of the protein
• Zinc ions form an important part of the structure of carbonic anhydrase - enzyme necessary for the metabolism of carbon dioxide. Zinc ions are a permanent part of the enzymes active site

Question 6

What are precursor enzymes?

Answer 6

• enzymes produced in inactive form = inactive precursor enzymes
• precursor enzymes often need to undergo a change in shape to the active site to be activated

Question 7

How does precursor activation work?

Answer 7

• achieved by the addition of a cofactor
• before the cofactor is added, the precursor protein is an apoenzyme
• the activated enzyme with a cofactor is a haloenzyme
• sometimes the change in the tertiary structure is brought about by the action of another enzyme
• sometimes a change in conditions can activate a precursor enzyme