Information on EC 2.5.1.44 - homospermidine synthase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
2.5.1.44
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RECOMMENDED NAME
GeneOntology No.
homospermidine synthase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
2 putrescine = sym-homospermidine + NH3 + H+
show the reaction diagram
the reaction of this enzyme occurs in three steps: i. NAD-dependent dehydrogenation of putrescine, ii. transfer of the 4-aminobutylidene group from dehydroputrescine to a second molecule of putrescine, iii. reduction of the imine intermediate to form homospermidine. Hence the overall reaction is transfer of a 4-aminobutyl group. In the presence of putrescine, spermidine can function as a donor of the aminobutyl group, in which case, propane-1,3-diamine is released instead of ammonia. Differs from EC 2.5.1.45, homospermidine synthase, spermidine-specific, which cannot use putrescine as donor of the aminobutyl group
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putrescine + spermidine = sym-homospermidine + propane-1,3-diamine
show the reaction diagram
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
aminobutyl group transfer
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
Tropane, piperidine and pyridine alkaloid biosynthesis
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Biosynthesis of secondary metabolites
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SYSTEMATIC NAME
IUBMB Comments
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 2.5.1.45, homospermidine synthase (spermidine-specific), which cannot use putrescine as donor of the aminobutyl group.
CAS REGISTRY NUMBER
COMMENTARY hide
76106-84-8
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
Acinetobacter tartarogenes
N.C.I.B. 10028
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Manually annotated by BRENDA team
grass pea
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Manually annotated by BRENDA team
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UniProt
Manually annotated by BRENDA team
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
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sym-homospermidine is required for normal growth of the alpha-proteobacterium Rhizobium leguminosarum. Symhomospermidine can be replaced, for growth restoration, by the structural analogues spermidine and symnorspermidine, suggesting that the symmetrical or unsymmetrical form, and carbon backbone length are not critical for polyamine function in growth
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
2 putrescine
sym-homospermidine + NH3
show the reaction diagram
putrescine + 1,3-diaminopropane
homospermidine + spermidine
show the reaction diagram
putrescine + 1,6 diaminohexane
homospermidine + N-(4-aminobutyl)-1,6-diaminohexane
show the reaction diagram
putrescine + 1,7-diaminoheptane
homospermidine + N-(4-aminobutyl)-1,7-diaminoheptane
show the reaction diagram
putrescine + cadaverine
homospermidine + N-(4-aminobutyl)-1,5-diaminopentane
show the reaction diagram
spermidine
homospermidine + putrescine + 1,3-diaminopropane
show the reaction diagram
spermidine + 1,6-diaminohexane
homospermidine + N-(4-aminobutyl)-1,6-diaminohexane
show the reaction diagram
spermidine + cadaverine
homospermidine + N-(4-aminobutyl)-1,5-diaminopentane
show the reaction diagram
spermidine + putrescine
homospermidine + 1,3-diaminopropane
show the reaction diagram
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
2 putrescine
sym-homospermidine + NH3
show the reaction diagram
COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
NADP+
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68% of the activity with NAD+
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Na+
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less effective than K+ in activation
Rb+
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less effective than K+ in activation
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
1,3-Diaminopropane
1,5-Diaminopentane
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weak inhibition
cadaverine
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iodoacetamide
Acinetobacter tartarogenes
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preincubation, 1 mM, 30 min prior to assay causes 50% inhibition
N-ethylmaleimide
spermidine
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additional information
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4-aminobutyraldehyde, postulated intermediate, no inhibition
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.001 - 0.018
NAD+
0.05 - 3
putrescine
1.5
spermidine
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in presence of 1 mM putrescine
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
1.18 - 8
putrescine
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
4.6 - 28.6
putrescine
155
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.00025
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0.0038
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8.41
Acinetobacter tartarogenes
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
8.7
Acinetobacter tartarogenes
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assay at, optimal pH
8.8 - 9
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in 50 mM potassium phosphate or Bis-Tris-propane buffers
8.8
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assay at, optimal pH
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
37
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reaction linear up to 60 min and is proportional to the amount of enzyme protein (0.1-0.5 mg)
45
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increasing activity up to 45°C, sharp decrease at higher temperatures
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
73000
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gel filtration
75000
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gel filtration
100000
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gel filtration
102000
Acinetobacter tartarogenes
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gel filtration
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
-18
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storage as acetone dry-powder, stable for several months
STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
-18°C, storage as acetone dry-powder, without significant loss of activity
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1°C, 20 mM, Tris/HCl, pH 7.5, 10 mM 2-mercaptoethanol, 0.5 mM putrescine, 0.02% NaN3
Acinetobacter tartarogenes
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
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Acinetobacter tartarogenes
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224fold; overexpressed Escherichia coli strain BL21
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partial, 100fold
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expressed in Escherichia coli. The host Escherichia coli cells without the recombinant homospermidine synthase orthologue accumulate putrescine, cadaverine and spermidine and expression of each the homospermidine syntase orthologue in Escherichia coli results in accumulation of homospermidine in the host cells
overexpressed in Escherichia coli BL21, which originally does not possess HSS activity. 40-50% of the soluble protein in crude extracts are detected as homospermidine synthase
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