ID 2.5.1.126 DE norspermine synthase. AN long-chain polyamine synthase. CA norspermidine + S-adenosyl 3-(methylsulfanyl)propylamine = H(+) + CA norspermine + S-methyl-5'-thioadenosine. CC -!- The enzyme, characterized from the thermophilic archaeon Pyrobaculum CC aerophilum, can also synthesize norspermidine from propane-1,3- CC diamine and thermospermine from spermidine (with lower activity). CC -!- The long-chain polyamines stabilize double-stranded DNA at high CC temperatures. CC -!- In contrast to EC 2.5.1.127, this enzyme does not accept norspermine CC as a substrate. DR A2BIX4, SPEE1_HYPBU; Q8ZXM4, SPEE_PYRAE ; Q9UXE4, SPEE_SACS2 ; DR Q5SK28, SPEE_THET8 ; //