coenzyme /kō·en″zīm/ [L, cum, together with, en, in, zyme, ferment] , a nonprotein substance that combines with an apoenzyme to form a complete enzyme or holoenzyme. Coenzymes include some of the vitamins, such as B1 and B2, and have smaller molecules than enzymes. Coenzymes are dialyzable and heat-stable and usually dissociate readily from the protein portions of the enzymes with which they combine. See also acetylcoenzyme A.
