This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: polyamine biosynthesis, triaminic polyamine biosynthesis
|Superclasses:||Biosynthesis → Amines and Polyamines Biosynthesis|
Expected Taxonomic Range: cellular organisms
sym-homospermidine is an uncommon triaminic polyamine found in bacteria, fungi, higher plants as well as amphibians, arthropods and mammalian tissues. The biosynthetic pathway has recently been worked out in higher plants with the isolation of the enzyme homospermidine synthase [Kaiser99].
The homospermidine synthase enzyme catalyzes the first biosynthetic step in pyrrolizidine alkaloids (PA) found in certain angiosperm families. homospermidine synthase detected in PA producing plants catalyzes the formation of the polyamine sym-homospermidine, the unique precursor of necine base moiety of all PA's representing 1-hydroxmethylpyrrolizidine derivatives [Frolich07].
In Nicotiana tabacum and Senecio, it has been demonstrated that the HSS enzyme evolved from deoxyhypusine synthase and possessed all the enzyme characteristics except it had lost the ability to bind elF5A [Ober99a]. The deoxyhypusine synthase enzyme however was able to carry out both sym-homospermidine as well as hypusine biosynthesis.
Frolich07: Frolich C, Ober D, Hartmann T (2007). "Tissue distribution, core biosynthesis and diversification of pyrrolizidine alkaloids of the lycopsamine type in three Boraginaceae species." Phytochemistry 68(7);1026-37. PMID: 17320124
Ober99: Ober D, Hartmann T (1999). "Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase." Proc Natl Acad Sci U S A 96(26);14777-82. PMID: 10611289
Ober99a: Ober D, Hartmann T (1999). "Deoxyhypusine synthase from tobacco. cDNA isolation, characterization, and bacterial expression of an enzyme with extended substrate specificity." J Biol Chem 274(45);32040-7. PMID: 10542236
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