MetaCyc Enzyme: spermidine synthase

Gene: SRM Accession Number: G-9019 (MetaCyc)

Species: Homo sapiens

Subunit composition of spermidine synthase = [SRM]2
         spermidine synthase subunit = SRM

The human spermine synthase has been purified to homogeneity and partially characterized [Kajander89]. The enzyme was found in all tissues studied. Very high spermidine synthase activity was present in the pancreas, where it surpassed spermine synthase activity 25-fold. Human kidney contained the highest spermine synthase activity, and in both the kidney and the placenta spermine synthase surpassed spermidine synthase activity 3- and 5-fold respectively.

Thus there are large differences in both synthase activities in various tissues [Kajander89].

Gene Citations: [Wahlfors90]

Molecular Weight of Polypeptide: 33.825 kD (from nucleotide sequence), 35 kD (experimental) [Kajander89 ]

Molecular Weight of Multimer: 62 kD (experimental) [Kajander89]

pI: 5.1 [Kajander89]

Unification Links: ArrayExpress:P19623 , ModBase:P19623 , PhosphoSite:P19623 , PhylomeDB:P19623 , Pride:P19623 , Protein Model Portal:P19623 , SMR:P19623 , String:9606.ENSP00000366156 , Swiss-Model:P19623 , UniProt:P19623

Relationship Links: Entrez-Nucleotide:PART-OF:M34338 , InterPro:IN-FAMILY:IPR001045 , InterPro:IN-FAMILY:IPR029063 , Panther:IN-FAMILY:PTHR11558 , PDB:Structure:2O05 , PDB:Structure:2O06 , PDB:Structure:2O07 , PDB:Structure:2O0L , PDB:Structure:3RW9 , Pfam:IN-FAMILY:PF01564 , Prosite:IN-FAMILY:PS01330 , Prosite:IN-FAMILY:PS51006

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Enzymatic reaction of: spermidine synthase

EC Number:

putrescine + S-adenosyl 3-(methylthio)propylamine <=> spermidine + S-methyl-5'-thioadenosine + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

This reaction is reversible.

In Pathways: superpathway of polyamine biosynthesis II , L-methionine salvage cycle III , spermidine biosynthesis I

Kinetic Parameters:

Km (μM)
S-adenosyl 3-(methylthio)propylamine


Kajander89: Kajander EO, Kauppinen LI, Pajula RL, Karkola K, Eloranta TO (1989). "Purification and partial characterization of human polyamine synthases." Biochem J 259(3);879-86. PMID: 2730590

Wahlfors90: Wahlfors J, Alhonen L, Kauppinen L, Hyvonen T, Janne J, Eloranta TO (1990). "Human spermidine synthase: cloning and primary structure." DNA Cell Biol 9(2);103-10. PMID: 2344393

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Thu Oct 8, 2015, biocyc13.