Spermidine/spermine synthases (IPR001045)

Short name: Spermi_synthase

Overlapping homologous superfamilies

Family relationships


The nearly ubiquitous polyamines (putrescine, spermidine and spermine) are polycationic mediators of cell proliferation and differentiation whose functions likely provide both stability and neutralisation for nucleic acids. The following polyamine biosynthetic enzymes are evolutionary related [PMID: 9517003]:

  • Spermidine synthase (EC: (putrescine aminopropyltransferase). It catalyzes the last step in the biosynthesis of spermidine from arginine and methionine; the conversion of putrescine to spermidine using decarboxylated S-adenosylmethionine as the cofactor.
  • Spermine synthase (EC: (spermidine aminopropyltransferase). It converts spermidine into spermine using decarboxylated S-adenosylmethionine as the cofactor.
  • Putrescine N-methyltransferase (EC: It catalyzes a step in the biosynthesis of nicotine in plants; the methylation of putrescine to N- methylputrescine using S-adenosylmethionine as the cofactor.

The Thermotoga maritima spermidine synthase monomer consists of two domains: an N-terminal domain composed of six beta-strands, and a Rossmann-like C- terminal domain. The larger C-terminal catalytic core domain consists of a seven-stranded beta-sheet flanked by nine alpha helices. This domain resembles a topology observed in a number of nucleotide and dinucleotide-binding enzymes, and in S-adenosyl-L-methionine (AdoMet)- dependent methyltransferase (MTases) [PMID: 11731804].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0003824 catalytic activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.