What is the function of a coenzyme


Synonym: coenzyme

1 definition

A Coenzyme is a low molecular weight organic molecule that is essential for the catalytic activity of an enzyme.

2 mechanism

Coenzymes have a variety of functions, including the transfer of hydrogen in redox reactions, transamination (PALP) and transfer of methyl groups. As auxiliary molecules, coenzymes can temporarily take up and release groups transferred by the enzyme in a catalysis. They thus exercise a transport function and regulate the metabolic processes.

3 classification

Coenzymes can be divided into two ways.

3.1 According to the type of groups transferred

A coenzyme always transports the same specific groups of atoms. Relevant sub-categories of this type are:

3.1.1 Group-transmitting coenzymes

This group of coenzymes transports chemical groups, e.g. phosphoric acid residues or amino groups.
Examples of such coenzymes are:

3.1.2 Redox Coenzymes

A coenzyme that releases or accepts hydrogen or electrons during redox reactions. Since oxidation always goes hand in hand with reduction, these coenzymes serve to act as necessary reaction partners in a redox reaction.
Examples of redox coenzymes are:

  • Liponamide: transfers two hydrogen atoms
  • NAD and NADP: transfers a hydride ion (H.-)
  • Iron-sulfur complex: transfers an electron

3.2 According to the nature of the enzyme relationship

A coenzyme can behave differently than the enzyme it uses. A distinction is made between:

3.2.1 Prosthetic groups

Prosthetic groups are organic molecules that are firmly bound to the enzyme, remain bound to the enzyme before, during and after the reaction and are also regenerated there again.
Examples of prosthetic groups are:

3.2.2 Soluble coenzymes

Soluble coenzymes, also called cosubstrates, are bound like substrates during the reaction and are released again in a chemically modified form after the reaction, but, unlike substrates, are then regenerated again in a subsequent reaction independent of the reaction cycle and made available for a new reaction .
Examples of soluble coenzymes are:

4 background

Many coenzymes are derived from vitamins and cannot be synthesized in the body. Other coenzymes synthesized in the body are often derived from nucleotides. The complete enzyme made up of protein and low molecular weight coenzyme is called a holoenzyme.