Pyruvate dehydrogenase is a large, highly integrated complex containing many copies of three distinct enzymes. there are five coenzymes involved in its catalytic activity: nad+ , fad , coenzyme a, lipoamide, and thiamine pyrophosphate (tpp or tdp). the coenzymes can be classified depending on how they participate in an enzymatic reaction. a coenzyme prosthetic group is tightly bound to the enzyme and remains bound during the catalytic cycle. the original coenzymes are regenerated during the catalytic cycle. on the other hand, a coenzyme cosubstrate is loosely bound to an enzyme and dissociates in an altered form as part of the catalytic cycle. its original form is regenerated not by the cycle, but by another enzyme. which are coenzyme prosthetics? a. nad+ b. tpp or tdp c. lipoamide d. fad e. coenzyme a