Information on EC 2.5.1.45 - homospermidine synthase (spermidine-specific)

for references in articles please use BRENDA:EC2.5.1.45
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EC Tree
IUBMB Comments
A eukaryotic enzyme found in plants. The reaction occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: (a) NAD+-dependent dehydrogenation of spermidine to 4-iminobutan-1-amine, (b) attack by water forming 4-aminobutanal (and releasing propane-1,3-diamine), and (c) condensation of 4-aminobutanal with purescine, which forms homospermidine and restores NAD+. This enzyme is more specific than EC 2.5.1.44, homospermidine synthase, which is found in bacteria, as it cannot use putrescine as donor of the 4-aminobutyl group. Forms part of the biosynthetic pathway of the poisonous pyrrolizidine alkaloids of the ragworts (Senecio).
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The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
Synonyms
homospermidine synthase, HSS, HSS1, synthase, homospermidine, synthase, homospermidine (Senecio vernalis root gene HSS1), more
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
spermidine + putrescine = sym-homospermidine + propane-1,3-diamine
show the reaction diagram
the reaction of this enzyme occurs in three steps: i. NAD-dependent dehydrogenation of spermidine, ii. transfer of the 4-aminobutylidene group from dehydrospermidine to putrescine, iii. reduction of the imine intermediate to form homospermidine. Hence the overall reaction is transfer of a 4-aminobutyl group. This enzyme is more specific than EC 2.5.1.44, homospermidine synthase, which is found in bacteria, as it cannot use putrescine as donor of the 4-aminobutyl group. Forms part of the biosynthetic pathway of the poisonous pyrrolizidine alkaloids of the ragworts, Senecio
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PATHWAY SOURCE
PATHWAYS
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