EC - Homospermidine synthase (spermidine-specific)

  IntEnz view ENZYME view

IntEnz Enzyme Nomenclature


Accepted name:
homospermidine synthase (spermidine-specific)
Systematic name:
spermidine:putrescine 4-aminobutyltransferase (propane-1,3-diamine-forming)




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 dehydrospermidine, (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, 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).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0050514


  1. Böttcher, F., Ober, D. and Hartmann, T.
    Biosynthesis of pyrrolizidine alkaloids: putrescine and spermidine are essential substrates of enzymatic homospermidine formation.
    Can. J. Chem. 72 : 80-85 (1994).
  2. Ober, D. and Hartmann, T.
    Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase.
    Proc. Natl. Acad. Sci. USA 96 : 14777-14782 (1999). [PMID: 10611289]
  3. Ober, D., Harms, R. and Hartmann, T.
    Cloning and expression of homospermidine synthase from Senecio vulgaris: a revision.
    Phytochemistry 55 : 311-316 (2000). [PMID: 11117877]

[EC created 2001]