Non-protein part of an enzyme molecule; either a coenzyme or a metal ion. Essential for catalytic activity. The enzyme protein without its prosthetic group is the apoenzyme and is catalytically inactive. With the prosthetic group, it is known as the holo-enzyme.
A heat-stable metal ion or an organic group (other than an amino acid) that is covalently bonded to the apoenzyme protein. It is required for enzyme function. The term is now largely obsolete.
A nonprotein , organic, chemical group attached to a protein, heme in the hemoglobin molecule.
A nonprotein component of an enzyme (or other body protein) that is necessary to the activity of that enzyme or protein.
The non-amino acid component of a conjugated protein; usually the portion of an enzyme that is not an amino acid.