Reaction: (1) 2 putrescine = sym-homospermidine + NH3 + H+
(2) putrescine + spermidine = sym-homospermidine + propane-1,3-diamine
For reaction pathway click here.
dehydroputrescine = 4-iminobutan-1-amine
sym-homospermidine = N-(4-aminobutyl)butane-1,4-diamine
putrescine = butane-1,4-diamine
Systematic name: putrescine:putrescine 4-aminobutyltransferase (ammonia-forming)
Comments: The reaction of this enzyme occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: NAD+-dependent dehydrogenation of putrescine (1a), transfer of the 4-aminobutylidene group from dehydroputrescine to a second molecule of putrescine (1b) and reduction of the imine intermediate to form homospermidine (1c). Hence the overall reaction is transfer of a 4-aminobutyl group. Differs from EC 18.104.22.168, homospermidine synthase (spermidine-specific), which cannot use putrescine as donor of the aminobutyl group.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 76106-84-8
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