 Cofactor (biochemistry)

A enzyme cofactor is a nonprotein component required for the activity of an enzyme or another protein. It can be a metal ion or an organic component; an organic helper is often called a coenzyme. A tightly bound component and a diffusible reaction partner play different roles, even when both are necessary for the overall reaction. The protein component without its required enzyme cofactor can therefore have a different activity from the complete functional assembly. ^[ref]