https://doi.org/10.1351/goldbook.C01128
Organic molecules (cf. @C01126@) or ions (usually metal ions) that are required by an @E02159@ of its activity. They may be attached either loosely or tightly @P04893@) to the enzyme. A cofactor binds with its associated protein (apoenzymes), which is functionally inactive, to form the active enzyme (@H02836@).