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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2 putrescine = sym-homospermidine + NH3 + H+
the reaction mechanism emphasizes cation-Pi interaction through a conserved Trp residue as a key stabilizer of high energetic transition states. The enzyme has two distinct substrate binding sites, one of which is highly specific for putrescine. Enzyme HSS features a side pocket in the direct vicinity of the active site formed by conserved amino acids and a potential substrate discrimination, guiding, and sensing mechanism
the reaction mechanism emphasizes cation-Pi interaction through a conserved Trp residue as a key stabilizer of high energetic transition states. The enzyme has two distinct substrate binding sites, one of which is highly specific for putrescine. Enzyme HSS features a side pocket in the direct vicinity of the active site formed by conserved amino acids and a potential substrate discrimination, guiding, and sensing mechanism
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.
in Paramecium, a bacterial homospermidine synthase replaces the eukaryotic genes encoding spermidine biosynthesis, S-adenosylmethionine decarboxylase and spermidine synthase. The Paramecium tetraurelia macronuclear genome does not encode any homologues of S-adenosylmethionine decarboxylase and spermidine synthase. Many eukaryotic parasites have lost the entire spermidine biosynthetic pathway but have in all cases retained the deoxyhypusine synthase gene required to post-translationally modify eIF5A. Replacement of spermidine with homospermidine is compatible with hypusine modification of eIF5A, loss of dependence on S-adenosylmethionine decarboxylase for spermidine biosynthesis has the benefit ofdispensing with the use of metabolically expensive S-adenosyl-L-methionine and the methionine salvage pathway required to rescue methionine from methylthioadenosine, the coproduct of spermidine synthase
bacterial homospermidine synthase is highly conserved and is proposed to be evolutionarily related to carboxy(nor)spermidine dehydrogenase, EC 1.5.1.43. Despite of the low amino acid sequence identity between plant HSS and bacterial HSS of about 12% (Senecio vulgaris vs. Blastochloris viridis HSS), a conserved fold within the three dimensional structure of bacterial HSS might be responsible for the similarity of the reaction mechanism
in Paramecium, a bacterial homospermidine synthase replaces the eukaryotic genes encoding spermidine biosynthesis, S-adenosylmethionine decarboxylase and spermidine synthase. The Paramecium tetraurelia macronuclear genome does not encode any homologues of S-adenosylmethionine decarboxylase and spermidine synthase. Many eukaryotic parasites have lost the entire spermidine biosynthetic pathway but have in all cases retained the deoxyhypusine synthase gene required to post-translationally modify eIF5A. Replacement of spermidine with homospermidine is compatible with hypusine modification of eIF5A, loss of dependence on S-adenosylmethionine decarboxylase for spermidine biosynthesis has the benefit ofdispensing with the use of metabolically expensive S-adenosyl-L-methionine and the methionine salvage pathway required to rescue methionine from methylthioadenosine, the coproduct of spermidine synthase
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
ann enzyme knockout mutant does not contain neither homospermidine nor 4-aminobutilcadaverine and is more sensitive to salinity than the wild-type, and plants inoculated with the mutant bacteria have lower nodule fresh weight than with the wild-type
ann enzyme knockout mutant does not contain neither homospermidine nor 4-aminobutilcadaverine and is more sensitive to salinity than the wild-type, and plants inoculated with the mutant bacteria have lower nodule fresh weight than with the wild-type
Paramecium tetraurelia performs spermidine biosynthesis by aminopropylation of putrescine with production of methylthioadenosine from decarboxylated S-adenosylmethionine, it accumulates homospermidine and shows absence of a methionine salvage pathway. Paramecium tetraurelia encodes four paralogues of bacterial homospermidine synthase, and at least one of those paralogues is enzymatically active in vitro. Paramecium accumulates homospermidine, suggesting it replaces spermidine for growth. Paramecium tetraurelia encodes four paralogues of bacterial homospermidine synthase, and at least one of those paralogues is enzymatically active in vitro. Homospermidine supports eukaryotic cell growth and proliferation
Paramecium tetraurelia performs spermidine biosynthesis by aminopropylation of putrescine with production of methylthioadenosine from decarboxylated S-adenosylmethionine, it accumulates homospermidine and shows absence of a methionine salvage pathway. Paramecium tetraurelia encodes four paralogues of bacterial homospermidine synthase, and at least one of those paralogues is enzymatically active in vitro. Paramecium accumulates homospermidine, suggesting it replaces spermidine for growth. Paramecium tetraurelia encodes four paralogues of bacterial homospermidine synthase, and at least one of those paralogues is enzymatically active in vitro. Homospermidine supports eukaryotic cell growth and proliferation
homospermidine synthase contributes to salt tolerance in free-living Rhizobium tropici and in symbiosis with Phaseolus vulgaris. Homospermidine is involved in the stress tolerance of fast-growing rhizobia and in the bacteroid protection from environmental changes. The enzyme seems to be involved in nodule organogenesis, the enzyme HSS is not required for normal growth of Rhizobium tropici but provides tolerance to salt stress, growth kinetics in wild-type and mutant strains, overview
homospermidine synthase contributes to salt tolerance in free-living Rhizobium tropici and in symbiosis with Phaseolus vulgaris. Homospermidine is involved in the stress tolerance of fast-growing rhizobia and in the bacteroid protection from environmental changes. The enzyme seems to be involved in nodule organogenesis, the enzyme HSS is not required for normal growth of Rhizobium tropici but provides tolerance to salt stress, growth kinetics in wild-type and mutant strains, overview
the structure of the bacterial enzyme does not possess a lysine residue in the active center and does not form an enzyme-substrate Schiff base intermediate as observed for deoxyhypusine synthase. The active site is not formed by the interface of two subunits but resides within one subunit of the bacterial enzyme. The enzyme has two distinct substrate binding sites, one of which is highly specific for putrescine. Enzyme HSS features a side pocket in the direct vicinity of the active site formed by conserved amino acids and a potential substrate discrimination, guiding, and sensing mechanism. Three-dimensional structure analysis, PDB ID 4PLP, and substrate binding analysis
one molecule of putrescine is oxidized by NAD+ to form enzyme-bound 4-aminobutyraldehyde. This intermediate reacts with a second molecule of putrescine to form a Schiff base which is reduced by NADH (formed from NAD+ in the first part of the reaction) to give homospermidine
one molecule of putrescine is oxidized by NAD+ to form enzyme-bound 4-aminobutyraldehyde. This intermediate reacts with a second molecule of putrescine to form a Schiff base which is reduced by NADH (formed from NAD+ in the first part of the reaction) to give homospermidine
as partially purified enzymes have been used in the assay the dependence on spermidine for the homospermidine synthesis may have been overlooked. If these enzymes should proof to be spermidine-dependent like other enzymes from plant sources, they must be classified as EC 2.5.1.45
as partially purified enzymes have been used in the assay the dependence on spermidine for the homospermidine synthesis may have been overlooked. If these enzymes should proof to be spermidine-dependent like other enzymes from plant sources, they must be classified as EC 2.5.1.45
the enzyme has two distinct substrate binding sites, one of which is highly specific for putrescine. Enzyme HSS features a side pocket in the direct vicinity of the active site formed by conserved amino acids and a potential substrate discrimination, guiding, and sensing mechanism. The enzyme is capable of catalyzing side reactions to produce a variety of N-aminobutyl-linked triamines utilizing putrescine together with respective linear diamines with C3 to C7 carbon chains, overview. Bacterial HSS does not produce sym-norspermidine from two 1,4-diaminopropanes
one molecule of putrescine is oxidized by NAD+ to form enzyme-bound 4-aminobutyraldehyde. This intermediate reacts with a second molecule of putrescine to form a Schiff base which is reduced by NADH (formed from NAD+ in the first part of the reaction) to give homospermidine
one molecule of putrescine is oxidized by NAD+ to form enzyme-bound 4-aminobutyraldehyde. This intermediate reacts with a second molecule of putrescine to form a Schiff base which is reduced by NADH (formed from NAD+ in the first part of the reaction) to give homospermidine
as partially purified enzymes have been used in the assay the dependence on spermidine for the homospermidine synthesis may have been overlooked. If these enzymes should proof to be spermidine-dependent like other enzymes from plant sources, they must be classified as EC 2.5.1.45
as partially purified enzymes have been used in the assay the dependence on spermidine for the homospermidine synthesis may have been overlooked. If these enzymes should proof to be spermidine-dependent like other enzymes from plant sources, they must be classified as EC 2.5.1.45
unique usage of NAD(H) as a prosthetic group. the cofactor is coordinated through hydrogen bonding via residues Ser21, Ile22, Ser230 (phosphate), Asp45, Val66 (adenosine), Ser92,Thr114, Ala161, Asn162, and Pro163 (nicotineamide riboside). The phosphate-binding motif (18GFGSIG23) is located in the loop connecting beta-strand 2 and alpha-helix A of the Rossmann fold. The adenosine part of NAD+ is bound via loop regions located between beta-strand 4, 5, 6 and alpha-helix C, D, E. Nicotineamide-riboside-binding residues are found in loop regions between beta-strand 7 and 8 and alpha-helix F and O
unique usage of NAD(H) as a prosthetic group. the cofactor is coordinated through hydrogen bonding via residues Ser21, Ile22, Ser230 (phosphate), Asp45, Val66 (adenosine), Ser92,Thr114, Ala161, Asn162, and Pro163 (nicotineamide riboside). The phosphate-binding motif (18GFGSIG23) is located in the loop connecting beta-strand 2 and alpha-helix A of the Rossmann fold. The adenosine part of NAD+ is bound via loop regions located between beta-strand 4, 5, 6 and alpha-helix C, D, E. Nicotineamide-riboside-binding residues are found in loop regions between beta-strand 7 and 8 and alpha-helix F and O
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
the BvHSS structure is solved from crystals belonging to space group P212121 with bound NAD+, PDB ID 4PLP. Crystals from BvHSS and BvHSS variants with bound NAD+ in complex with various polyamines all belong to space group P22121 with cell parameters in approximately the same order of magnitude. Structure analysis
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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
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
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
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
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
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
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
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
construction of a mutant strain Rt hss::omega,Spr of Rhizobium tropici strain Rt CIAT899 impaired in the synthesis of homospermidine, neither homospermidine nor 4-aminobutilcadaverine are detected in the free-living mutant bacteria and in nodules of plants inoculated with the mutant strain
construction of a mutant strain Rt hss::omega,Spr of Rhizobium tropici strain Rt CIAT899 impaired in the synthesis of homospermidine, neither homospermidine nor 4-aminobutilcadaverine are detected in the free-living mutant bacteria and in nodules of plants inoculated with the mutant strain
Homospermidine synthase of Rhodopseudomonas viridis: substrate specificity and effects of the heterologously expressed enzyme of polyamine metabolism of Escherichia coli
Different polyamine pathways from bacteria have replaced eukaryotic spermidine biosynthesis in ciliates Tetrahymena thermophila and Paramecium tetaurelia