thermospermine synthase

{{Infobox enzyme

| Name = Thermospermine synthase

| EC_number = 2.5.1.79

| CAS_number =

| GO_code =

| image =

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| caption =

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Thermospermine synthase ({{EC number|2.5.1.79}}, TSPMS, ACL5 (ACAULIS5), SAC51) is an enzyme with systematic name S-adenosylmethioninamine:spermidine 3-aminopropyltransferase (thermospermine synthesizing).{{cite journal | vauthors = Romer P, Faltermeier A, Mertins V, Gedrange T, Mai R, Proff P | title = Investigations about N-aminopropyl transferases probably involved in biomineralization | journal = Journal of Physiology and Pharmacology | volume = 59 Suppl 5 | pages = 27–37 | date = November 2008 | pmid = 19075322 }}{{cite journal | vauthors = Knott JM, Römer P, Sumper M | title = Putative spermine synthases from Thalassiosira pseudonana and Arabidopsis thaliana synthesize thermospermine rather than spermine | journal = FEBS Letters | volume = 581 | issue = 16 | pages = 3081–6 | date = June 2007 | pmid = 17560575 | doi = 10.1016/j.febslet.2007.05.074 | doi-access = free }}{{cite journal | vauthors = Muñiz L, Minguet EG, Singh SK, Pesquet E, Vera-Sirera F, Moreau-Courtois CL, Carbonell J, Blázquez MA, Tuominen H | title = ACAULIS5 controls Arabidopsis xylem specification through the prevention of premature cell death | journal = Development | volume = 135 | issue = 15 | pages = 2573–82 | date = August 2008 | pmid = 18599510 | doi = 10.1242/dev.019349 | doi-access = free }} This enzyme catalyses the following chemical reaction

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

This enzyme is required for correct xylem specification through regulation of the lifetime of the xylem elements.