A fluorescent analog of nicotinamide adenine dinucleotide.

Nicotinamide 1,N(6)-ethenoadenine dinucleotide, a fluorescent analog of the coenzyme nicotinamide adenine dinucleotide, has been synthesized by the reaction of chloroacetaldehyde with the coenzyme. The technical fluorescence emission maximum of the analog is 410 nm, upon excitation at 300 nm. Its fluorescence yield is about 8% of that of the 1,N(6)-ethenoadenine 5'-phosphate, and its fluorescence lifteime is shorter. Upon hydrolysis of the modified coenzyme analog with Neurospora crassa NADase or phosphodiesterase I at room temperature, the intensity of fluorescence was increased 10-fold, corresponding to separation of the nicotinamide and ethenoadenine rings. The spectroscopic results with nicotinamide 1,N(6)-ethenoadenine dinucleotide are consistent with the concept of an intramolecular interaction between the modified adenine and pyridine moieties of the dinucleotide that is disrupted by enzymatic hydrolysis. The fluorescent analog showed reasonable activity as a substitute for NAD(+) in four different dehydrogenase-catalyzed reactions.