Holoenzyme

Holoenzyme is a catalytically active enzyme that consists of apoenzyme and cofactor. Cofactors can make reactions that cannot be done by standard twenty amino acids. Cofactors are divided in two groups:

• metals (Zn²⁺, Mg²⁺, Ni²⁺ , Mo, Se, Mn, K⁺),
  
• coenzymes.

Use of the same coenzyme usually means that enzymes catalyse similar mechanisms .

Sigigma 70 and RNA Polymerase II is an example of a holoenzyme used in transcription of prokaryotes.