Deoxyhypusine synthase

Deoxyhypusine synthase (EC 2.5.1.46, spermidine:eIF5A-lysine 4-aminobutyltransferase (propane-1,3-diamine-forming)) is an enzyme with systematic name (eIF5A-precursor)-lysine:spermidine 4-aminobutyltransferase (propane-1,3-diamine-forming). This enzyme catalyses the following chemical reaction

[eIF5A-precursor]-lysine + spermidine ⇌ [eIF5A-precursor]-deoxyhypusine + propane-1,3-diamine (overall reaction)(1a) spermidine + NAD⁺ ⇌ dehydrospermidine + NADH(1b) dehydrospermidine + [enzyme]-lysine ⇌ N-(4-aminobutylidene)-[enzyme]-lysine + propane-1,3-diamine(1c) N-(4-aminobutylidene)-[enzyme]-lysine + [eIF5A-precursor]-lysine ⇌ N-(4-aminobutylidene)-[eIF5A-precursor]-lysine + [enzyme]-lysine(1d) N-(4-aminobutylidene)-[eIF5A-precursor]-lysine + NADH + H+ ⇌ [eIF5A-precursor]-deoxyhypusine + NAD⁺

The eukaryotic initiation factor eIF5A contains a hypusine residue that is essential for activity.