As we shall see in our examination of the biosynthesis of squalene, Coenzyme A (CoA), sometimes called "active acetate", is the principle species involved in the transfer of acetate from various catabolic pathways to metabolic ones.

• The pantothenic acid incorporated into CoA is one of the B vitamins.
  

• The business end of the molecule is the thiol group, shown in red, which becomes bound to acetate, forming acetyl CoA.
  • Thiol esters are more reactive than ordinary oxygen esters, owing to less delocalization of electrons between the sulfur and the carbonyl (which would require 2p - 3p overlap)

  • This has led to the description of the CO-S bond as "energy rich". However, the terminology is a ridiculous here as in the case of phosphates.

  Here is a structure of CoA from a semi-empirical MO calculation:

  

• The association of the disease beri-beri with thiamine deficiency is well-known.

• Thiamine is found in the husks of rice and other grains, and polishing away the brown husk of rice to make white rice removes this essential nutrient.

• Hence the inclusion of brown rice with the so-called "macrobiotic" diet of the health food fans.
  

• Thiamine is converted in organisms using it to the pyrophosphate, which is the active coenzyme.

• It is involved primarily with decarboxylases, such as pyruvate decarboxylase, and also is used by transketolases.