Coenzyme

A coenzyme is an organic, non-protein molecule that binds to an enzyme and is required for its catalytic activity. Most coenzymes are derived from vitamins and aid enzymes by participating in the chemical reactions themselves. Coenzymes are typically not permanently bound and can dissociate from the enzyme after the reaction, in contrast to tightly bound prosthetic groups.

Coenzymes function as carriers of electrons, atoms, or functional groups. During catalysis, they shuttle these moieties between substrates and enzymes, enabling the transformation of substrates into products. After the reaction, they are regenerated to their original form by cellular processes, allowing repeated use in metabolism.

Common examples include:

- NAD+ and NADP+ (nicotinamide adenine dinucleotide and its phosphate), derived from niacin (vitamin B3); central to redox reactions in energy metabolism and biosynthesis.

- FAD and FMN (flavin adenine dinucleotide and flavin mononucleotide), derived from riboflavin (vitamin B2); participate in various oxidation-reduction reactions.

- Coenzyme A (CoA), derived from pantothenic acid (vitamin B5); transfers acyl groups in fatty acid and carbohydrate metabolism.

- Thiamine pyrophosphate (TPP), derived from thiamine (vitamin B1); involved in decarboxylation and aldehyde transfer reactions.

- Pyridoxal phosphate (PLP), derived from pyridoxine (vitamin B6); essential for amino group transfer.

Other coenzymes include biotin, lipoamide, and tetrahydrofolate, each supporting specific metabolic processes.

Source and deficiency: Coenzymes are synthesized from vitamins or their precursors; inadequate vitamin intake or enzymatic defects can impair coenzyme formation, leading to metabolic disturbances. Adequate vitamin nutrition supports proper coenzyme function and energy metabolism.