KEGG   ENZYME: 2.5.1.45
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)
Sysname
spermidine:putrescine 4-aminobutyltransferase (propane-1,3-diamine-forming)
Reaction(IUBMB)
spermidine + putrescine = sym-homospermidine + propane-1,3-diamine [RN:R01919]
Reaction(KEGG)
R01919
Substrate
spermidine [CPD:C00315];
putrescine [CPD:C00134]
Product
sym-homospermidine [CPD:C06366];
propane-1,3-diamine [CPD:C00986]
Comment
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).
History
EC 2.5.1.45 created 2001
Orthology
K21300  homospermidine synthase (spermidine-specific)
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 72:80-85 (1994)
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 96:14777-82 (1999)
DOI:10.1073/pnas.96.26.14777
  Sequence
Reference
3  [PMID:11117877]
  Authors
Ober D, Harms R, Hartmann T
  Title
Cloning and expression of homospermidine synthase from Senecio vulgaris: a revision.
  Journal
Phytochemistry 55:305-9 (2000)
DOI:10.1016/s0031-9422(00)00267-3
Other DBs
ExplorEnz - The Enzyme Database: 2.5.1.45
IUBMB Enzyme Nomenclature: 2.5.1.45
ExPASy - ENZYME nomenclature database: 2.5.1.45
BRENDA, the Enzyme Database: 2.5.1.45
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