A nonpeptide organic molecule or metal ion that binds tightly and specifically with a protein and is required for its activity, such as heme in hemoglobin. See also coenzyme.
a coenzyme that is tightly bound to the enzyme
a small organic molecule (non-amino acid) that is bound tightly to a protein
a metal ion or small molecule (other than an amino acid) that associates with a protein and is essential to the its biochemical functioning; its attachment to the protein may be either covalent or noncovalent.
A prosthetic group is a non-protein (non-amino acid) component of a conjugated protein. The prosthetic group may be organic (such as a vitamin, sugar, or lipid) or inorganic (such as a metal ion). Prosthetic groups usually bond covalently to their protein.