Meaning of COFACTOR in English


An atom, organic molecule, or molecular group that is necessary for the catalytic activity (see catalysis ) of many enzyme s.

A cofactor may be tightly bound to the protein portion of an enzyme and thus be an integral part of its functional structure, or it may be only loosely associated and free to diffuse away from the enzyme. Cofactors of the integral kind include metal atoms

such as iron , copper , or magnesium

or moderately sized organic molecules called prosthetic groups; many of the latter contain a metal atom, often in a coordination complex (see transition element ). Removal of the cofactor from the enzyme's structure causes loss of its catalytic activity. Loosely associated cofactors are called coenzyme s; examples include most members of the vitamin B complex . Rather than directly contributing to the catalytic ability of an enzyme, coenzymes participate with the enzyme in the catalytic reaction. Sometimes this distinction in definition is no longer made, and coenzyme is used in the broader sense of cofactor .

Britannica English dictionary.      Английский словарь Британика.