Spermine synthase

{{Infobox enzyme

| Name = Spermine synthase

| EC_number = 2.5.1.22

| CAS_number = 74812-43-4

| GO_code =

| image =

| width =

| caption =

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Spermine synthase ({{EC number|2.5.1.22}}, spermidine aminopropyltransferase, spermine synthetase) is an enzyme that converts spermidine into spermine.{{cite journal | vauthors = Hibasami H, Borchardt RT, Chen SY, Coward JK, Pegg AE | title = Studies of inhibition of rat spermidine synthase and spermine synthase | journal = The Biochemical Journal | volume = 187 | issue = 2 | pages = 419–28 | date = May 1980 | doi = 10.1042/bj1870419 | pmid = 7396856 | pmc = 1161808 }}{{cite journal | vauthors = Pajula RL, Raina A, Eloranta T | title = Polyamine synthesis in mammalian tissues. Isolation and characterization of spermine synthase from bovine brain | journal = European Journal of Biochemistry | volume = 101 | issue = 2 | pages = 619–26 | date = November 1979 | pmid = 520313 | doi = 10.1111/j.1432-1033.1979.tb19756.x | doi-access = free }} This enzyme catalyses the following chemical reaction

: S-adenosylmethioninamine + spermidine $\backslash rightleftharpoons$ S-methyl-5'-thioadenosine + spermine

Spermine synthase is an enzyme involved in polyamine biosynthesis. It is present in all eukaryotes and plays a role in a variety of biological functions in plants{{cite journal | vauthors = Imamura T, Fujita K, Tasaki K, Higuchi A, Takahashi H | title = Characterization of spermidine synthase and spermine synthase--The polyamine-synthetic enzymes that induce early flowering in Gentiana triflora | journal = Biochemical and Biophysical Research Communications | volume = 463 | issue = 4 | pages = 781–6 | date = August 2015 | pmid = 26056006 | doi = 10.1016/j.bbrc.2015.06.013 }} Its structure consists of two identical monomers of 41 kDa with three domains each, creating a homodimer formed via dimerization. The interactions between one of the three domains, the N-terminals of the monomers, is responsible for dimerization as that is where the active site is located; the central terminal consisting of four β- strands structurally forming a lid for the third domain, the C-terminal domain.{{cite journal | vauthors = Pegg AE, Michael AJ | title = Spermine synthase | journal = Cellular and Molecular Life Sciences | volume = 67 | issue = 1 | pages = 113–21 | date = January 2010 | pmid = 19859664 | pmc = 2822986 | doi = 10.1007/s00018-009-0165-5 }}