EC	2.5.1.79
Accepted name:	thermospermine synthase
Reaction:	S-adenosyl 3-(methylsulfanyl)propylamine + spermidine = S-methyl-5′-thioadenosine + thermospermine + H+
Glossary:	thermospermine = N1-[3-(3-aminopropylamino)propyl]butane-1,4-diamine S-adenosyl 3-(methylsulfanyl)propylamine = (3-aminopropyl){[(2S,3S,4R,5R)-5-(6-amino-9H-purin-9-yl)-3,4-dihydroxytetrahydrofuran-2-yl]methyl}methylsulfonium
Other name(s):	TSPMS; ACL5; SAC51; S-adenosyl 3-(methylthio)propylamine:spermidine 3-aminopropyltransferase (thermospermine synthesizing)
Systematic name:	S-adenosyl 3-(methylsulfanyl)propylamine:spermidine 3-aminopropyltransferase (thermospermine-forming)
Comments:	This plant enzyme is crucial for the proper functioning of xylem vessel elements in the vascular tissues of plants [3].
References:	1.  Romer, P., Faltermeier, A., Mertins, V., Gedrange, T., Mai, R. and Proff, P. Investigations about N-aminopropyl transferases probably involved in biomineralization. J. Physiol. Pharmacol. 59 Suppl 5 (2008) 27–37. [PMID: 19075322] 2.  Knott, J.M., Romer, P. and Sumper, M. Putative spermine synthases from Thalassiosira pseudonana and Arabidopsis thaliana synthesize thermospermine rather than spermine. FEBS Lett. 581 (2007) 3081–3086. [PMID: 17560575] 3.  Muniz, L., Minguet, E.G., Singh, S.K., Pesquet, E., Vera-Sirera, F., Moreau-Courtois, C.L., Carbonell, J., Blazquez, M.A. and Tuominen, H. ACAULIS5 controls Arabidopsis xylem specification through the prevention of premature cell death. Development 135 (2008) 2573–2582. [PMID: 18599510]
[EC 2.5.1.79 created 2010, modified 2013]
EC	2.5.1.126
Accepted name:	norspermine synthase
Reaction:	S-adenosyl 3-(methylsulfanyl)propylamine + norspermidine = S-methyl-5′-thioadenosine + norspermine
Glossary:	norspermidine = bis(3-aminopropyl)amine norspermine = N,N′-bis(3-aminopropyl)-1,3-propanediamine spermidine = N-(3-aminopropyl)-1,4-butanediamine thermospermine = N-{3-[(3-aminopropyl)amino]propyl}-1,4-butanediamine
Other name(s):	long-chain polyamine synthase (ambiguous)
Systematic name:	S-adenosyl 3-(methylsulfanyl)propylamine:norspermidine 3-aminopropyltransferase
Comments:	The enzyme, characterized from the thermophilic archaeon Pyrobaculum aerophilum, can also synthesize norspermidine from propane-1,3-diamine and thermospermine from spermidine (with lower activity). The long-chain polyamines stabilize double-stranded DNA at high temperatures. In contrast to EC 2.5.1.127, caldopentamine synthase, this enzyme does not accept norspermine as a substrate.
References:	1.  Knott, J.M. Biosynthesis of long-chain polyamines by crenarchaeal polyamine synthases from Hyperthermus butylicus and Pyrobaculum aerophilum. FEBS Lett. 583 (2009) 3519–3524. [PMID: 19822146]
[EC 2.5.1.126 created 2014]
EC	2.5.1.127
Accepted name:	caldopentamine synthase
Reaction:	S-adenosyl 3-(methylsulfanyl)propylamine + norspermine = S-methyl-5′-thioadenosine + caldopentamine
Glossary:	caldopentamine = N-(3-aminopropyl)-N′-{3-[(3-aminopropyl)amino]propyl}-1,3-propanediamine norspermidine = N-(3-aminopropyl)-1,4-butanediamine norspermine = N,N′-bis(3-aminopropyl)-1,3-propanediamine spermidine = N-(3-aminopropyl)-1,4-butanediamine thermospermine = N-{3-[(3-aminopropyl)amino]propyl}-1,4-butanediamine
Other name(s):	long-chain polyamine synthase (ambiguous)
Systematic name:	S-adenosyl 3-(methylsulfanyl)propylamine:norspermine 3-aminopropyltransferase
Comments:	The enzyme, characterized from the thermophilic archaeon Hyperthermus butylicus, can also synthesize norspermine from norspermidine and thermospermine from spermidine (with lower activity). The long-chain polyamines stabilize double-stranded DNA at high temperatures. In contrast to EC 2.5.1.23, sym-norspermidine synthase and EC 2.5.1.126, norspermine synthase, this enzyme shows no activity with propane-1,3-diamine.
References:	1.  Knott, J.M. Biosynthesis of long-chain polyamines by crenarchaeal polyamine synthases from Hyperthermus butylicus and Pyrobaculum aerophilum. FEBS Lett. 583 (2009) 3519–3524. [PMID: 19822146]
[EC 2.5.1.127 created 2014]