Catalysis of the reaction: -lysine + spermidine = -deoxyhypusine + propane-1,3-diamine. Four sub-reactions have been identified,in which the intermediates remain tightly associated with the enzyme: spermidine + NAD+ = dehydrospermidine + NADH; dehydrospermidine + -lysine = N-(4-aminobutylidene)--lysine + propane-1,3-diamine; N-(4-aminobutylidene)--lysine + -lysine = N-(4-aminobutylidene)--lysine + -lysine; N-(4-aminobutylidene)--lysine + NADH + H+ = -deoxyhypusine + NAD+.
spermidine dehydrogenase