noun.
A nonproteinaceous organic substance that usually contains a vitamin or mineral and combines with a specific protein, the apoenzyme, to form an active enzyme system.
the GNU version of the Collaborative International Dictionary of English
a molecule that is essential for the activity of some enzymes; it may exist free in solution within a living organism, but functions by binding to an enzyme to assist in catalyzing a reaction. The molecule itself may be temporarily changed during the reaction, but is ultimately restored to its original form. Many vitamins function as coenzymes.
noun.
Any small molecule that is necessary for the functioning of an enzyme.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
a small molecule (not a protein but sometimes a vitamin) essential for the activity of some enzymes
Word Usage
"~ Low-Dose CoQ10 Supplements Won't Ease Parkinson's (HealthDay) -- "Low doses of an antioxidant called coenzyme Q10 (CoQ10), sold as a dietary supplement, do not appear to improve Parkinson's disease symptoms, a German study finds.""