EC 18.104.22.168 - Homospermidine synthase (spermidine-specific)
IntEnz Enzyme Nomenclature
11236 [IUBMB]putrescineputrescineName origin: UniProt - CHECKED (C)Formula: C4H14N2
Charge: 2ChEBI compound status: CHECKED (C)spermidinespermidineName origin: UniProt - CHECKED (C)Formula: C7H22N3
Charge: 3ChEBI compound status: CHECKED (C)=propane-1,3-diaminepropane-1,3-diamineName origin: UniProt - CHECKED (C)Formula: C3H12N2
Charge: 2ChEBI compound status: CHECKED (C)
A eukaryotic enzyme found in plants. The reaction occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: (a) NAD+-dependent dehydrogenation of spermidine to dehydrospermidine, (b) attack by water forming 4-aminobutanal (and releasing propane-1,3-diamine), and (c) condensation of 4-aminobutanal with purescine, which forms homospermidine and restores NAD+. This enzyme is more specific than EC 22.214.171.124, homospermidine synthase, which is found in bacteria, as it cannot use putrescine as donor of the 4-aminobutyl group. Forms part of the biosynthetic pathway of the poisonous pyrrolizidine alkaloids of the ragworts (Senecio).
Links to other databases
Biosynthesis of pyrrolizidine alkaloids: putrescine and spermidine are essential substrates of enzymatic homospermidine formation.Can. J. Chem. 72 : 80-85 (1994).
Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase.Proc. Natl. Acad. Sci. USA 96 : 14777-14782 (1999). [PMID: 10611289]
Cloning and expression of homospermidine synthase from Senecio vulgaris: a revision.Phytochemistry 55 : 311-316 (2000). [PMID: 11117877]
[EC 126.96.36.199 created 2001]