ID   2.5.1.45
DE   Homospermidine synthase (spermidine-specific).
CA   Spermidine + putrescine = sym-homospermidine + propane-1,3-diamine.
CF   NAD(+).
CC   -!- The reaction of this enzyme occurs in three steps:
CC       (1) NAD(+)-dependent dehydrogenation of spermidine.
CC       (2) Transfer of the 4-aminobutylidene group from dehydrospermidine to
CC       a second molecule of putrescine.
CC       (3) Reduction of the imine intermediate to form homospermidine.
CC   -!- Hence the overall reaction is transfer of a 4-aminobutyl group.
CC   -!- This enzyme is more specific than EC 2.5.1.44 which is found in
CC       bacteria, as it cannot use putrescine as donor of the 4-aminobutyl
CC       group.
CC   -!- Forms part of the biosynthetic pathway of the poisonous pyrrolizidine
CC       alkaloids of the ragworts (Senecio).
DR   Q9SC13, HSS1_SENVE ;  Q9M4B0, HSS1_SENVU ;  P60038, HSS2_SENVE ;
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