The Enzyme Database

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EC 2.5.1.44     
Accepted name: homospermidine synthase
Reaction: (1) 2 putrescine = sym-homospermidine + NH3
(2) spermidine + putrescine = sym-homospermidine + propane-1,3-diamine
For diagram of reaction, click here
Glossary: sym-homospermidine = N1-(4-aminobutyl)butane-1,4-diamine
putrescine = butane-1,4-diamine
Other name(s): putrescine:putrescine 4-aminobutyltransferase (ammonia-forming)
Systematic name: putrescine/spermidine:putrescine 4-aminobutyltransferase
Comments: The reaction of this bacterial enzyme occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: (a) NAD+-dependent dehydrogenation of either putrescine or spermidine, forming 4-iminobutan-1-amine or (E)-(4-aminobutylidene)(3-aminopropyl)amine, respectively, (b) attack by water forming 4-aminobutanal (and releasing ammonia or propane-1,3-diamine, respectively), and (c) condensation of 4-aminobutanal with putrescine, which forms homospermidine and restores NAD+. Differs from the eukaryotic enzyme 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.  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]
3.  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.
4.  Krossa, S., Faust, A., Ober, D. and Scheidig, A.J. Comprehensive Structural Characterization of the Bacterial Homospermidine Synthase-an Essential Enzyme of the Polyamine Metabolism. Sci. Rep. 6:19501 (2016). [PMID: 26776105]
[EC 2.5.1.44 created 1999, modified 2001]
 
 


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