cofactori

Cofactori, in biochemistry, are non-protein chemical components that are required for the catalytic activity of many enzymes. In Italian biochemistry literature, cofactors are referred to as cofactori. They are not part of the enzyme’s amino acid sequence but are essential for function; some cofactors remain bound to the enzyme, while others associate transiently during the reaction.

Cofactors are generally classified as inorganic cofactors, such as metal ions (for example Mg2+, Fe2+, Zn2+), and organic cofactors, which include coenzymes and prosthetic groups. Coenzymes are organic molecules that shuttle electrons or functional groups between enzymes, with examples including NAD+, FAD, CoA, and vitamins that serve as vitamin-derived cofactors. Prosthetic groups are cofactors that are tightly bound to the enzyme, such as heme in cytochromes or biotin in carboxylases.

Binding modes vary: some cofactors are tightly bound to form holoenzymes, while others act as cosubstrates that bind and dissociate after a reaction. Cofactors participate in catalysis by stabilizing charged intermediates, donating or accepting chemical groups, or facilitating redox reactions. Their presence can enable reactions that the polypeptide alone cannot perform.

Biological and medical relevance: cofactors influence the rates and outcomes of metabolic pathways, and deficiencies or defects in cofactor binding can impair enzyme activity and contribute to disease. Cofactor levels are affected by diet, nutrition, and cellular metabolism. See also coenzyme, prosthetic group, apoenzyme, holoenzyme.