Transferases;
Transferring alkyl or aryl groups, other than methyl groups;
Transferring alkyl or aryl groups, other than methyl groups (only sub-subclass identified to date)
BRITE hierarchy

[eIF5A-precursor]-lysine:spermidine 4-aminobutyltransferase (propane-1,3-diamine-forming)

[eIF5A-precursor]-lysine + spermidine = [eIF5A-precursor]-deoxyhypusine + propane-1,3-diamine (overall reaction) [RN:R05329];
(1a) spermidine + NAD+ = dehydrospermidine + NADH [RN:R07477];
(1b) dehydrospermidine + [enzyme]-lysine = N-(4-aminobutylidene)-[enzyme]-lysine + propane-1,3-diamine [RN:R07479];
(1c) N-(4-aminobutylidene)-[enzyme]-lysine + [eIF5A-precursor]-lysine = N-(4-aminobutylidene)-[eIF5A-precursor]-lysine + [enzyme]-lysine [RN:R07480];
(1d) N-(4-aminobutylidene)-[eIF5A-precursor]-lysine + NADH + H+ = [eIF5A-precursor]-deoxyhypusine + NAD+ [RN:R07478]

R05329 R07477 R07478 R07479 R07480
Reaction

[eIF5A-precursor]-lysine [CPD:C07281];
spermidine [CPD:C00315];
NAD+ [CPD:C00003];
dehydrospermidine [CPD:C15853];
[enzyme]-lysine [CPD:C07281];
N-(4-aminobutylidene)-[enzyme]-lysine [CPD:C15854];
N-(4-aminobutylidene)-[eIF5A-precursor]-lysine [CPD:C15854];
NADH [CPD:C00004];
H+ [CPD:C00080]

The eukaryotic initiation factor eIF5A contains a hypusine residue that is essential for activity. This enzyme catalyses the first reaction of hypusine formation from one specific lysine residue of the eIF5A precursor. The reaction occurs in four steps: NAD+-dependent dehydrogenation of spermidine (1a), formation of an enzyme-imine intermediate by transfer of the 4-aminobutylidene group from dehydrospermidine to the active site lysine residue (Lys329 for the human enzyme; 1b), transfer of the same 4-aminobutylidene group from the enzyme intermediate to the e1F5A precursor (1c), reduction of the e1F5A-imine intermediate to form a deoxyhypusine residue (1d). Hence the overall reaction is transfer of a 4-aminobutyl group. For the plant enzyme, homospermidine can substitute for spermidine and putrescine can substitute for the lysine residue of the eIF5A precursor. Hypusine is formed from deoxyhypusine by the action of EC 1.14.99.29, deoxyhypusine monooxygenase.

EC 2.5.1.46 provisional version created 1999 as EC 1.1.1.249 deleted 1999, revised and reinstated 2001 as EC 2.5.1.46