On the mechanism of the ethanol-diphosphopyridine nucleotide reaction

The explanation for the shift of the maximum of DPNH from 3400 Å to 3250 Å in the complex with alcohol dehydrogenase is derived from a consideration of environmental effects on the spectra of 1,4-dihydronicotinamides. It is concluded that a positively charged nitrogen in the form of an ammonium ion is located 3 Å from the nitrogen of the dihydropyridine ring and produces the shift by repulsion of the increased charge produced on the dihydropyridine nitrogen by light absorption. It is suggested that an ε{lunate}-amino group of lysine provides the ammonium ion and a transition state for the reduction of acetaldehyde by DPNH is written utilizing this suggestion and some other conclusions from the literature.