EC - Homospermidine synthase

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IntEnz Enzyme Nomenclature


Accepted name:
homospermidine synthase
Systematic name:
putrescine:putrescine 4-aminobutyltransferase (ammonia-forming)




The reaction of this enzyme occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: NAD+-dependent dehydrogenation of putrescine, transfer of the 4-aminobutylidene group from dehydroputrescine to a second molecule of putrescine and reduction of the imine intermediate to form homospermidine. Hence the overall reaction is transfer of a 4-aminobutyl group. Differs from EC, homospermidine synthase (spermidine-specific), which cannot use putrescine as donor of the aminobutyl group.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0047296
CAS Registry Number: 76106-84-8


  1. Tait, G.H.
    The formation of homospermidine by an enzyme from Rhodopseudomonas viridis.
    Biochem. Soc. Trans. 7: 199-200 (1979). [PMID: 437275]
  2. 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).
  3. Yamamoto, S., Nagata, S. and Kusaba, K.
    Purification and characterization of homospermidine synthase in Acinetobacter tartarogens ATCC 31105.
    J. Biochem. 114: 45-49 (1993). [PMID: 8407874]
  4. Srivenugopal, K.S. and Adiga, P.R.
    Enzymatic synthesis of sym-homospermidine in Lathyrus sativus T (grass pea) seedlings.
    Biochem. J. 190: 461-464 (1980). [PMID: 7470060]
  5. Ober, D., Tholl, D., Martin, W. and Hartmann, T.
    Homospermidine synthase of Rhodopseudomonas viridis: Substrate specificity and effects of the heterologously expressed enzyme on polyamine metabolism of Escherichia coli.
    J. Gen. Appl. Microbiol. 42: 411-419 (1996).
  6. 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]

[EC created 1999, modified 2001]