The Enzyme Database

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EC 2.5.1.44     
Accepted name: homospermidine synthase
Reaction: (1) 2 putrescine = sym-homospermidine + NH3 + H+
(2) putrescine + spermidine = sym-homospermidine + propane-1,3-diamine
For diagram of reaction, click here
Glossary: sym-homospermidine = N-(4-aminobutyl)butane-1,4-diamine
putrescine = butane-1,4-diamine
dehydroputrescine = 4-iminobutan-1-amine
Systematic name: putrescine:putrescine 4-aminobutyltransferase (ammonia-forming)
Comments: The reaction of this enzyme occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: NAD+-dependent dehydrogenation of putrescine, transfer of the 4-aminobutylidene group from dehydroputrescine to a second molecule of putrescine and reduction of the imine intermediate to form homospermidine. Hence the overall reaction is transfer of a 4-aminobutyl group. Differs from EC 2.5.1.45, homospermidine synthase (spermidine-specific), which cannot use putrescine as donor of the aminobutyl group.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 76106-84-8
References:
1.  Tait, G.H. The formation of homospermidine by an enzyme from Rhodopseudomonas viridis. Biochem. Soc. Trans. 7 (1979) 199–200. [PMID: 437275]
2.  Böttcher, F., Ober, D. and Hartmann, T. Biosynthesis of pyrrolizidine alkaloids: putrescine and spermidine are essential substrates of enzymatic homospermidine formation. Can. J. Chem. 72 (1994) 80–85.
3.  Yamamoto, S., Nagata, S. and Kusaba, K. Purification and characterization of homospermidine synthase in Acinetobacter tartarogens ATCC 31105. J. Biochem. 114 (1993) 45–49. [PMID: 8407874]
4.  Srivenugopal, K.S. and Adiga, P.R. Enzymatic synthesis of sym-homospermidine in Lathyrus sativus T (grass pea) seedlings. Biochem. J. 190 (1980) 461–464. [PMID: 7470060]
5.  Ober, D., Tholl, D., Martin, W. and Hartmann, T. Homospermidine synthase of Rhodopseudomonas viridis: Substrate specificity and effects of the heterologously expressed enzyme on polyamine metabolism of Escherichia coli. J. Gen. Appl. Microbiol. 42 (1996) 411–419.
6.  Ober, D. and Hartmann, T. Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase. Proc. Natl. Acad. Sci. USA 96 (1999) 14777–14782. [PMID: 10611289]
[EC 2.5.1.44 created 1999, modified 2001]
 
 


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