Coenzymes are necessary for the functioning of certain enzymes. They are relatively smaller than the enzymes they aid. They may either be loosely or strongly attached to a particular enzyme. Examples of coenzymes are adenosine triphosphate (ATP), cobalamins, and coenzyme A.
Coenzyme A (CoA, CoASH, or HSCoA) is a coenzyme known for its involvement in the transfer of acyl group in fatty acid metabolism and amino acid metabolism. CoA shuttles the acyl groups, such as the acetyl unit and as such is called acetyl coenzyme A (acetyl-CoA). When it is not attached to an acyl group it is referred simply to as CoASH or HSCoA. Thus, it is involved in the first step of the Krebs cycle, particularly the introduction of the acetyl group into the Krebs cycle to be oxidized for energy production.
The biosynthesis of CoA needs 4 molecules of adenine triphosphate from cysteine and pantothenate (vitamer of vitamin B5).1
Abbreviation / Acronym: CoA
Chemical formula: C21H36N7O16P3S
1 Leonardi R, Zhang YM, Rock CO, Jackowski S (2005). "Coenzyme A: back in action". Progress in Lipid Research 44 (2-3): 125–153.