Cofactors, coenzymes and prosthetic groups

What are cofactors?

Inorganic enzyme helpers

* Transfer atoms or groups from one reaction to another

Or

* Form part of the active site

Where are cofactors obtained?

* Via diet as minerals (Fe, Ca, Cl, Zn ions)


* Eg - amylase has a Cl ion for a correct AS

What are coenzymes?

Organic cofactors

* A non-protein organic molecule, not permanently attached to an enzyme, but needed to allow the enzyme to function.

Where are coenzymes derived from?

Vitamins

* Eg - vitamin B3 synthesises NAD, coenzyme responsible for transferring H atoms between respiration molecules
* NADP is derived from B3 and has a similar role in photosynthesis

What is a prosthetic group?

* A cofactor that forms a permanent part of a functioning protein molecule
* Eg - Zn ions form a part of carbonic anhydrase (metabolism of CO2)

What is precursor activation?

* Where an enzyme must be activated to begin its function
* Need to have its 3• changed by adding a cofactor
* Before it's added the precursor is apoenzyme
* After it's added it is a holoenzyme

How can the tertiary structure of an enzyme be changed for precursors?

* An enzyme split bonds in the molecule
* Changes in temp and pH (zymogens or proenzymes)