EC Number   |
General Information |
Reference |
|---|
   2.5.1.44 | evolution |
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 |
739672 |
| 2.5.1.44 | evolution |
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 |
-, 739108 |
| 2.5.1.44 | malfunction |
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 |
-, 739378 |
| 2.5.1.44 | malfunction |
deletion of hss has no effect on polyamine levels in an otherwise wild-type strain, but in the CASDH mutant, it completely abolishes the increased Hspd levels. The DELTAhss mutant is also unaffected for prototrophic growth in the wild type, and this mutation does not alter the growth phenotypes of the DELTACASDH mutant |
-, 742792 |
| 2.5.1.44 | malfunction |
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 |
704662 |
| 2.5.1.44 | metabolism |
essential enzyme of the bacterial polyamine metabolism |
739672 |
| 2.5.1.44 | metabolism |
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 |
-, 739108 |
| 2.5.1.44 | more |
homospermidine is a structural analogue of spermidine that is one methylene group longer, rendering homospermidine symmetrical |
-, 739108 |
| 2.5.1.44 | more |
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 |
739672 |
| 2.5.1.44 | physiological function |
deletion of HSS has no effect on polyamine levels in an otherwise wild-type strain. In the CASDH mutant, lacking carboxyspermidine dehydrogenase activity, it completely abolishes the increased homospermidine levels. The HSS mutant is also unaffected for prototrophic growth in the wild type, and the mutation does not alter the growth phenotypes of the CASDH mutant |
-, 742792 |
