| Type: | Family | Name: | Spermidine/spermine synthases |
| Description: | The nearly ubiquitous polyamines (putrescine, spermidine and spermine) arepolycationic 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 []:Spermidine synthase () (putrescine aminopropyltransferase). It catalyzes the last step in the biosynthesis of spermidine from arginine andmethionine; the conversion of putrescine to spermidine using decarboxylated S-adenosylmethionine as the cofactor.Spermine synthase () (spermidine aminopropyltransferase). It converts spermidine into spermine using decarboxylated S-adenosylmethionineas the cofactor.Putrescine N-methyltransferase (). 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. Thisdomain resembles a topology observed in a number of nucleotide and dinucleotide-binding enzymes, and in S-adenosyl-L-methionine (AdoMet)-dependent methyltransferase (MTases) []. | Short Name: | Spermi_synthase |
