Types of Coenzyme

Most reactions that take place in your body are regulated by the presence of proteins known as enzymes. Sometimes the actions of these enzymes are enhanced by other molecules called coenzymes. Many coenzymes are called vitamin-derived coenzymes, which are formed from the vitamins that are part of our diet. Water soluble vitamins typically function as the precursors to coenzymes. These include the B-vitamins and vitamin C. In addition to those derived from vitamins, there is another group of coenzymes known as metabolite coenzymes, usually made from nucleotides. Coenzymes act as agents for transferring different groups such as electrons or molecules during reactions.

Vitamins are the precursors for many coenzymes. (Image: PeoGeo/iStock/Getty Images)

Electron Transfer Coenzymes

Some coenzymes function by ferrying electrons or negative charges to enhance a reaction. Vitamins B-2, B-3 and C are all precursors of electron-carrying coenzymes. Vitamin B-2, or riboflavin, is the precursor for the flavin coenzymes flavin mononucleotide, or FMN, and flavin adenine dinucleotide, or FAD. Their main function is to accept and store electrons within proteins. Vitamin B-3, on the other hand, is the precursor for the nicotinamide coenzymes, nicotinamide adenine dinucleotide, or NAD, and nicotinamide adenine dinucleotide 2'-phosphate, or NADP, which carry electrons between different proteins. Vitamin C, or ascorbic acid, acts as an electron donor, changing in the process to dehydroascorbic acid. This reaction is important for the production of bile acid and the break down of tyrosine.

Vitamin B-12-derived Coenzymes

Methylcobalamin and 5'-deoxyadenosylcobalamin are two coenzymes formed from vitamin B-12 or cobalamin. Methylcobalamin is required for the production of methionine from homocysteine, while 5'-deoxyadenosylcobalamin has the role of changing the molecular arrangement of the metabolic product of some amino acids.

Coenzyme from Vitamin B-5

Vitamin B-5, or pantothenic acid, is used to make coenzyme A, often termed CoA. This has a free sulfur-containing group that can attach and move carbon compounds. Reactions that utilize pantothenic acid derived coenzymes include the production of fatty acids.

Metabolite Coenzymes

The most common metabolite coenzyme is adenosine triphosphate, or ATP. There are four reactions involving ATP, each involving the movement of a part of the ATP molecule. An adenosine monophospate or AMP group is transferred in the reaction that produces 5-phosphoribosyl-1-pyrophosphate, while an adenosine diphosphate or ADP group is transferred when glucose-6-phosphate is made. Two reactions require the transfer of a phosphoryl group, one to facilitate the production of S-adenosyle methionine from methionine, and the other, the production of glutamine synthetase-O-AMP.

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