https://doi.org/10.1351/goldbook.C01128
Organic molecules (cf. @[email protected]) or ions (usually metal ions) that are required by an @[email protected] of its activity. They may be attached either loosely or tightly @[email protected]) to the enzyme. A cofactor binds with its associated protein (apoenzymes), which is functionally inactive, to form the active enzyme (@[email protected]).