Coenzymes and Cofactors - Enzymes mayor may not have a nonprotein molecule attached to them. Some enzymes contain covalently bound carbohydrate groups, which do not affect the catalytic activity, but may influence enzyme stability or solubility. Many enzymes have metal ions, while some others possess low weight organic molecules; these are called cofactors, and are essential for enzyme activity.

An organic cofactor is commonly known as coenzyme. Cofactors and coenzymes may be covalently or noncovalently attached to the protein molecule, called apoenzyme.