Coenzyme

A substance that enhances the action of an enzyme. (An enzyme is a protein that functions as a catalyst to mediate and speed a chemical reaction). Coenzymes are small molecules. They cannot by themselves catalyze a reaction but they can help enzymes to do so. In technical terms, coenzymes are organic nonprotein molecules that bind with the protein molecule (apoenzyme) to form the active enzyme (holoenzyme). A number of the water-soluble vitamins such as vitamins B1, B2 and B6 serve as coenzymes.

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A substance (excluding solo metal ions) that enhances or is necessary for the action of enzymes; coenzymes are of smaller molecular size than the enzymes themselves, are dialyzable and relatively heat-stable, and are usually easily dissociable from the protein portion of the enzyme; several vitamins are c. precursors. SYN: cofactor (1).

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co·en·zyme (')kō-'en-.zīm n a thermostable nonprotein compound that forms the active portion of an enzyme system after combination with an apoenzyme compare ACTIVATOR (1)

co·en·zy·mat·ic (.)kō-.en-zə-'mat-ik, -(.)zī- adj

co·en·zy·mat·i·cal·ly -i-k(ə-)lē adv

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n.

a nonprotein organic compound that, in the presence of an enzyme, plays an essential role in the reaction that is catalysed by the enzyme. Coenzymes, which frequently contain the B vitamins in their molecular structure, include coenzyme A, FAD, and NAD.

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co·en·zyme (ko-enґzīm) an organic nonprotein molecule, frequently a phosphorylated derivative of a water-soluble vitamin, that binds with the protein molecule (apoenzyme) to form the active enzyme (holoenzyme).