Reduction of nicotinamide adenine dinucleotides by sodium cyanoborohydride

The relatively slow reduction of NAD+ and NADP+ by sodium cyanoborohydride leads to formation of the enzymically active form of NADH and NADPH. This reaction could be useful as a simple procedure to enzymically introduce a specific label into substrates when tritiated or deuterated cynanoborohydride is used for obtaining the reduced nicotinamide adenine dinucleotide.