Variations in Reduction of Tetrazolium Salts by Dehydrogenase Systems

Electronegative groups attached to either the N-2 phenyl or the N-3 phenyl rings are important in determining the readiness of enzymatic transfer of electrons to tetrazolium salts. The magnitude of the effects exerted by nitro, chloro, or cyano moieties are not identical when different dehydrogenase systems are compared. Furthermore, differences noted between several tetrazolium salts in any one dehydrogenase system are not necessarily reproduced when biochemical and histochemical preparations are compared. Although the reasons for these differences are not immediately apparent, preliminary observations with the succinoxidase system suggest that some clarification may follow closer inspection of site of transfer to tetrazolium salts in the chain of electron transport.