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{{Infobox enzyme
| Name = Homospermidine synthase
| EC_number = 2.5.1.44
| CAS_number = 76106-84-8
| IUBMB_EC_number = 2/5/1/44
| GO_code = 
| image = 
| width = 
| caption =
}}
'''Homospermidine synthase''' ({{EC number|2.5.1.44}}) is an [[enzyme]] with system name ''putrescine:putrescine 4-aminobutyltransferase (ammonia-forming)''.<ref>{{cite journal | title = The formation of homospermidine by an enzyme from ''Rhodopseudomonas viridis'' |author = Tait, G.H. |journal = Biochem. Soc. Trans. |year = 1979 |volume = 7 |pages = 199–200 |pmid = 437275 | issue = 1}}</ref><ref>{{cite journal | title = Biosynthesis of pyrrolizidine alkaloids: putrescine and spermidine are essential substrates of enzymatic homospermidine formation |author = B&ouml;ttcher, F., Ober, D. and Hartmann, T. |journal = Can. J. Chem. |year = 1994 |volume = 72 |pages = 80–85 |pmid = | doi = 10.1139/v94-013 }}</ref><ref>{{cite journal | title = Purification and characterization of homospermidine synthase in ''Acinetobacter tartarogens'' ATCC 31105 |author = Yamamoto, S., Nagata, S. and Kusaba, K. |journal = J. Biochem. |year = 1993 |volume = 114 |pages = 45–49 |pmid = 8407874 | issue = 1}}</ref><ref>{{cite journal | title = Enzymatic synthesis of ''sym''-homospermidine in ''Lathyrus sativus'' T (grass pea) seedlings |author = Srivenugopal, K.S. and Adiga, P.R. |journal = Biochem. J. |year = 1980 |volume = 190 |pages = 461–464 |pmid = 7470060 | issue = 2 | pmc = 1162113}}</ref><ref>{{cite journal | title = Homospermidine synthase of ''Rhodopseudomonas viridis'': Substrate specificity and effects of the heterologously expressed enzyme on polyamine metabolism of ''Escherichia coli'' |author = Ober, D., Tholl, D., Martin, W. and Hartmann, T. |journal = J. Gen. Appl. Microbiol. |year = 1996 |volume = 42 |pages = 411–419 |pmid = | doi = 10.2323/jgam.42.411 | issue = 5 }}</ref><ref>{{cite journal | title = Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase |author = Ober, D. and Hartmann, T. |journal = Proc. Natl. Acad. Sci. USA |year = 1999 |volume = 96 |pages = 14777–14782 |pmid = 10611289 | bibcode = 1999PNAS...9614777O | doi = 10.1073/pnas.96.26.14777 | issue = 26 | pmc = 24724}}</ref> This enzyme [[catalysis|catalyses]] the following [[chemical reaction]]

: (1) 2 [[putrescine]] <math>\rightleftharpoons</math> sym-homospermidine + NH<sub>3</sub> + H<sup>+</sup>
: (2) putrescine + [[spermidine]] <math>\rightleftharpoons</math> sym-homospermidine + propane-1,3-diamine

The reaction of this enzyme occurs in three steps.

== References ==
{{reflist}}

== External links ==
*{{MeshName|Homospermidine+synthase}}



[[Category:EC 2.5.1]]