A peptide is a molecule formed as a result of the linking of amino acid molecules by a peptide bond. The peptide is the backbone of polypeptides and subsequently, protein molecules. Enzymes are proteinous molecules that serve as biological catalysts. The prosthetic group of a protein/enzyme is a metallic attachment to the protein, which plays roles that are vital to its functioning.
However, when the peptide portion of a protein molecule lack its prosthetic group, the protein is called an APOPROTEIN.
