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Information on EC 2.5.1.45 - homospermidine synthase (spermidine-specific)
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2.5.1.45 homospermidine synthase (spermidine-specific)IUBMB Comments
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).
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The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
Synonyms
homospermidine synthase, HSS, HSS1, synthase, homospermidine, synthase, homospermidine (Senecio vernalis root gene HSS1), 
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
homospermidine synthase
HSS
synthase, homospermidine
-
-
-
-
synthase, homospermidine (Senecio vernalis root gene HSS1)
-
-
-
-
HSS
-
-
-
-
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
spermidine + putrescine = sym-homospermidine + propane-1,3-diamine
the reaction of this enzyme occurs in three steps: i. NAD-dependent dehydrogenation of spermidine, ii. transfer of the 4-aminobutylidene group from dehydrospermidine to putrescine, iii. reduction of the imine intermediate to form homospermidine. Hence the overall reaction is transfer of a 4-aminobutyl group. 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
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
aminobutyl group transfer
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-
-
-
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PATHWAY SOURCE
PATHWAYS
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SYSTEMATIC NAME
IUBMB Comments
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 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).
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CAS REGISTRY NUMBER
COMMENTARY
259168-77-9
-
76106-84-8
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
Eupatorium pauciflorum
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
-
-
-
?
putrescine + spermidine
N-(4-aminobutyl)butane-1,4-diamine + propane-1,3-diamine
the plant homospermidine synthase is essentially dependent on spermidine as aminobutyl donor and is unable to synthesize homospermidine from two molecules of putrescine
-
?
putrescine + spermidine
sym-homospermidine + propane-1,3-diamine
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-
-
-
?
putrescine + spermidine
sym-homospermidine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
Eupatorium pauciflorum
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-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
the plant homospermidine synthase is essentially dependent on spermidine as aminobutyl donor and is unable to synthesize homospermidine from two molecules of putrescine
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-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
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-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
first specific enzyme in the biosynthesis of the necine base moiety of pyrrolizidine alkaloids
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-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
first specific enzyme in the biosynthesis of the necine base moiety of pyrrolizidine alkaloids
-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
-
-
?
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
putrescine + spermidine
sym-homospermidine + propane-1,3-diamine
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-
-
-
?
putrescine + spermidine
sym-homospermidine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
Eupatorium pauciflorum
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-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
-
-
-
-
?
putrescine + spermine
sym-homospermine + propane-1,3-diamine
the plant homospermidine synthase is essentially dependent on spermidine as aminobutyl donor and is unable to synthesize homospermidine from two molecules of putrescine
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-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
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-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
first specific enzyme in the biosynthesis of the necine base moiety of pyrrolizidine alkaloids
-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
-
-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
-
first specific enzyme in the biosynthesis of the necine base moiety of pyrrolizidine alkaloids
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-
?
spermidine + putrescine
sym-homospermidine + propane-1,3-diamine
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-
-
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
NAD+
-
the NADH formed in the first part of the reaction, i.e. oxidative deamination of putrescine, is cosubstrate of the second part of the reaction, i.e. hydrogenation of an intermolecular Schiff's base between the semialdehyde in the reaction and the second putrescine unit
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INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.003
NAD+
-
NAD+ functions as an enzyme-bound redoxsystem that is reduced in the first and reoxidized in the second part of the overall reaction. It functions as a coenzyme and not a cosubstrate
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
0.047
0.062
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purified recombinant enzyme, pH and temperature not specified in the publication
0.136
-
purified recombinant enzyme, pH and temperature not specified in the publication
0.138
0.047
-
purified recombinant enzyme, pH and temperature not specified in the publication
0.138
-
purified recombinant enzyme, pH and temperature not specified in the publication
0.138
-
purified recombinant enzyme, pH and temperature not specified in the publication
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
-
young flower buds, but not mature flowers, express homospermidine synthase and are able to catalyze pyrrolizidine alkaloid biosynthesis
brenda
additional information
the enzyme is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem
brenda
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HSS is expressed exclusively in nonspecialized cells of the lower epidermis of young leaves and shoots
brenda
the enzyme is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem
brenda
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HSS expression in leaves directly underneath developing inflorescences
brenda
the enzyme is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem
brenda
plants activate a second site of HSS expression when inflorescences start to develop. HSS is localized in the bundle sheath cells of young leaves, which express the whole pyrrolizidine alkaloids biosynthetic route
brenda
from lower epidermis of leaf and stem, no activity in upper epidermis cells
brenda
from lower epidermis of leaf and stem, no activity in upper epidermis cells
brenda
from lower epidermis of leaf and stem, no activity in upper epidermis cells
brenda
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in young roots, HSS is detected only in cells of the endodermis, but in a later developmental stage, additionally in the pericycle
brenda
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gene expression is restricted to young root. Expressed uniformly in all cells of the root cortex parenchyma, but not within the endodermis and exodermis
brenda
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gene expression is restricted to young root. Expressed uniformly in all cells of the root cortex parenchyma, but not within the endodermis and exodermis
brenda
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expressed in the tips of aerial roots exclusively in mitotically active cells. Raphide crystal idioblasts present within the root apical meristem do not show expression
brenda
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in the roots of Eupatorium cannabinum, all cells of the cortex parenchyma are found to express HSS, but not the cells of the endodermis
brenda
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HSS is expressed exclusively in nonspecialized cells of the lower epidermis of young leaves and shoots
brenda
the enzyme is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem
brenda
the enzyme is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem
brenda
the enzyme is expressed only in the cells of the lower leaf epidermis and the epidermis of the stem
brenda
additional information
-
the tissue-specific expression of HSS in this boraginaceous species is unique with respect to plant organ, tissue, and cell type, expression patterns, immunohistochemic analysis and semiquantitative RT-PCR, overview
brenda
additional information
-
tissue-specific expression of enzyme HSS
brenda
additional information
-
the tissue-specific expression of HSS in this boraginaceous species is unique with respect to plant organ, tissue, and cell type, expression patterns, immunohistochemic analysis and semiquantitative RT-PCR, overview
brenda
additional information
-
not expressed in the aerial parts of the plant like buds, flower heads, leaves, or stems
brenda
additional information
-
the tissue-specific expression of HSS in this boraginaceous species is unique with respect to plant organ, tissue, and cell type, expression patterns, immunohistochemic analysis and semiquantitative RT-PCR, overview
brenda
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
malfunction
-
transgenic tobacco plants are generated expressing Senecio vernalis homospermidine synthase. Analyses of the polyamine content reveals that, in the transgenic plants, about 80% of spermidine is replaced by homospermidine without any conspicuous modifications of the phenotype. Tracer-feeding experiments and gas chromatographic analyses suggest that these high levels of homospermidine are not sufficient to explain the formation of alkaloid precursors
metabolism
physiological function
additional information
evolution
-
the gene encoding enzyme HSS origins from a single duplication event of a single-copy gene encoding deoxyhypusine synthase, DHS, EC 2.5.1.46. This duplication event was followed by several losses of a functional gene copy attributable to gene loss or pseudogenization. Statistical analyses of sequence data suggest that, in those lineages in which the gene copy was successfully recruited as HSS, the gene duplication event was followed by phases of various selection pressures, including purifying selection, relaxed functional constraints, and possibly positive Darwinian selection
evolution
-
the gene encoding enzyme HSS origins from a single duplication event of a single-copy gene encoding deoxyhypusine synthase, DHS, EC 2.5.1.46. This duplication event was followed by several losses of a functional gene copy attributable to gene loss or pseudogenization. Statistical analyses of sequence data suggest that, in those lineages in which the gene copy was successfully recruited as HSS, the gene duplication event was followed by phases of various selection pressures, including purifying selection, relaxed functional constraints, and possibly positive Darwinian selection
evolution
-
the gene encoding enzyme HSS origins from a single duplication event of a single-copy gene encoding deoxyhypusine synthase, DHS, EC 2.5.1.46. This duplication event was followed by several losses of a functional gene copy attributable to gene loss or pseudogenization. Statistical analyses of sequence data suggest that, in those lineages in which the gene copy was successfully recruited as HSS, the gene duplication event was followed by phases of various selection pressures, including purifying selection, relaxed functional constraints, and possibly positive Darwinian selection
evolution
-
the gene encoding enzyme HSS origins from a single duplication event of a single-copy gene encoding deoxyhypusine synthase, DHS, EC 2.5.1.46. This duplication event was followed by several losses of a functional gene copy attributable to gene loss or pseudogenization. Statistical analyses of sequence data suggest that, in those lineages in which the gene copy was successfully recruited as HSS, the gene duplication event was followed by phases of various selection pressures, including purifying selection, relaxed functional constraints, and possibly positive Darwinian selection
evolution
-
the gene encoding enzyme HSS origins from a single duplication event of a single-copy gene encoding deoxyhypusine synthase, DHS, EC 2.5.1.46. This duplication event was followed by several losses of a functional gene copy attributable to gene loss or pseudogenization. Statistical analyses of sequence data suggest that, in those lineages in which the gene copy was successfully recruited as HSS, the gene duplication event was followed by phases of various selection pressures, including purifying selection, relaxed functional constraints, and possibly positive Darwinian selection
metabolism
-
homospermidine synthase is the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis
metabolism
-
homospermidine synthase is the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis
metabolism
-
homospermidine synthase is the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis
metabolism
-
homospermidine synthase is the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis
metabolism
-
homospermidine synthase is the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis
metabolism
polymanines in Crotalaria are detectable only when the plants form nodules after infection with their rhizobial partner. But polyamines are synthesized by the plant not by the mcirosymbiont
metabolism
the enzyme is first specific enzyme in the biosynthesis of pyrrolizidine alkaloids
metabolism
the enzyme is first specific enzyme in the biosynthesis of pyrrolizidine alkaloids
metabolism
the enzyme is first specific enzyme in the biosynthesis of pyrrolizidine alkaloids, it is involved in the biosynthetic pathway of the lycopsamine-type polyamine indicine N-oxide
physiological function
RNAi knockdown of HSS in hairy roots by 60-80% results in a reduction of homospermidine by about 86% and of the major pyrrolizidine alkaloid components 7-acetylintermedine N-oxide and 3-acetylmyoscorpine N-oxide by approximately 60%
physiological function
the gene encoding isoform HSS1 is absent in some perennial ryegrass plants, and absence of the HSS1 gene is associated with lower levels of thesinine-rhamnoside pyrrolizidine alkaloids
additional information
exogenously applied nitrate has no impact on polyamine biosynthesis, and enzyme activity, but nodulation is inhibited at higher levels of nitrate by autoregulation
additional information
-
the Convulvulaceae species Ipomoea alba contains ipanguline-type polyamines. Detection of sites that are involved in optimizing HSS functionality
additional information
-
the Convulvulaceae species Ipomoea hederifolia contains ipanguline-type polyamines. Detection of sites that are involved in optimizing HSS functionality
additional information
-
the Convulvulaceae species Ipomoea meyeri contains ipanguline- and triangularine-type polyamines. Detection of sites that are involved in optimizing HSS functionality
additional information
-
the Convulvulaceae species Ipomoea neei contains ipanguline-type polyamines. Detection of sites that are involved in optimizing HSS functionality
additional information
-
the Convulvulaceae species Merremia quinquefolia contains ipanguline- and triangularine-type polyamines. Detection of sites that are involved in optimizing HSS functionality
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UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable).
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable). HSS1_SENVE
370
0
40726
Swiss-Prot
other Location (Reliability: 2)
HSS1_SENVU
370
0
40740
Swiss-Prot
other Location (Reliability: 2)
HSS2_SENVE
370
0
40733
Swiss-Prot
other Location (Reliability: 2)
I3Z8K6_BELBD
Belliella baltica (strain DSM 15883 / CIP 108006 / LMG 21964 / BA134)
323
0
36304
TrEMBL
-