Lysine 6-dehydrogenase (, L-lysine epsilon-dehydrogenase, L-lysine 6-dehydrogenase, LysDH) is an enzyme with systematic name L-lysine:NAD<sup>+</sup> 6-oxidoreductase (deaminating). This enzyme catalyses the following overall chemical reaction
The two substrates of this enzyme are L-lysine and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are (2S)-2,3,4,5-tetrahydropyridine-2-carboxylic acid (1), ammonia, reduced NADH, and a proton. The enzyme is highly specific for L-lysine as substrate, although S-(2-aminoethyl)-L-cysteine can act as a substrate, but more slowly.