The importance of being dimeric

Abstract
Why are there so many dimeric proteins and enzymes? While for heterodimers a functional explanation seems quite reasonable, the case of homodimers is more puzzling. The number of homodimers found in all living organisms is rapidly increasing. A thorough inspection of the structural data from the available literature and stability (measured from denaturation–renaturation experiments) allows one to suggest that homodimers can be divided into three main types according to their mass and the presence of a (relatively) stable monomeric intermediate in the folding–unfolding pathway. Among other explanations, we propose that an essential advantage for a protein being dimeric may be the proper and rapid assembly in the cellular milieu.