- A coenzyme is a prosthetic group (non-amino-acid) which, when bound to its apoenzyme, gives a holoenzyme.
- Coenzymes have an essential role in many biochemical reactions in metabolism
- Coenzymes often are co-substrates
- the vitamin cofactor adds as an acceptor or donor of functional groups that are removed or added to the actual substrate
- apoenzyme + coenzyme = holoenzyme