Coenzymes

 Coenzymes 

Small organic molecules, transporting the chemical groups from one enzyme to another, are known as coenzymes (e.g., thiamine, riboflavin, and folic acids). For example, the acetyl group carried by coenzyme A, the hydride ion carried by NAD or NADP", formyl, methenyl or methyl groups carried by folic acid, the phosphate group carried by adenosine triphosphate, and the methyl group carried by S-adenosylmethionine. 

As a result of enzymatic action, the coenzymes are changed chemically and so it is beneficial to consider them as a special class of substrates or second substrates, common to various enzymes. 

For example, coenzyme NADH is used by about 700 enzymes. There is usually continuous regeneration of the coenzymes leading to the maintenance of their concentrations (inside a cell), at steady level.

 For example, the pentose phosphate pathway methionine generates S-adenosylmethionine. This continuous regeneration denotes intensive use of even a small amount regenerates NADPH, pue adenosyltransferase coenzyme. 

For example, each day a human body converts its own weight into ATP energy. 

A functional enzyme, i.e., the holoenzyme, is made up of a protein protein part. Protein part is the apoenzyme and non-protein part is the coenzyme. 

Holoenzyme = Apoenzyme (Protein part) + Coenzyme (Non-protein part)

Coenzyme can be defined as the organic, non-protein, dialyzable, and low molecular weight substance, related with the functions of the enzyme. These are regarded as co-substrates or second substrates because their affinity with the enzyme is comparable to that of substrates.