KEGG   ENZYME: 2.5.1.45Help
Entry
EC 2.5.1.45                 Enzyme                                 

Name
homospermidine synthase (spermidine-specific)
Class
Transferases;
Transferring alkyl or aryl groups, other than methyl groups;
Transferring alkyl or aryl groups, other than methyl groups (only sub-subclass identified to date)
BRITE hierarchy
Sysname
spermidine:putrescine 4-aminobutyltransferase (propane-1,3-diamine-forming)
Reaction(IUBMB)
spermidine + putrescine = sym-homospermidine + propane-1,3-diamine [RN:R01919]
Reaction(KEGG)
Substrate
spermidine [CPD:C00315];
putrescine [CPD:C00134]
Product
sym-homospermidine [CPD:C06366];
propane-1,3-diamine [CPD:C00986]
Comment
The reaction of this enzyme occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: (a) NAD+-dependent dehydrogenation of spermidine, (b) transfer of the 4-aminobutylidene group from dehydrospermidine to putrescine and (c) reduction of the imine intermediate to form homospermidine. 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).
History
EC 2.5.1.45 created 2001
Reference
1
  Authors
Bottcher, F., Ober, D. and Hartmann, T.
  Title
Biosynthesis of pyrrolizidine alkaloids: putrescine and spermidine are essential substrates of enzymatic homospermidine formation.
  Journal
Can. J. Chem. 72 (1994) 80-85.
Reference
2  [PMID:10611289]
  Authors
Ober D, Hartmann T.
  Title
Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase.
  Journal
Proc. Natl. Acad. Sci. U. S. A. 96 (1999) 14777-82.
  Sequence
Reference
3
  Authors
Ober, D., Harms, R. and Hartmann, T.
  Title
Cloning and expression of homospermidine synthase from Senecio vulgaris: a revision.
  Journal
Phytochemistry 55 (2000) 311-316.
Other DBs
ExplorEnz - The Enzyme Database: 
IUBMB Enzyme Nomenclature: 
ExPASy - ENZYME nomenclature database: 
BRENDA, the Enzyme Database: 

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