homospermidine synthase (spermidine-specific)

Transferases;
Transferring alkyl or aryl groups, other than methyl groups;
Transferring alkyl or aryl groups, other than methyl groups (only sub-subclass identified to date)

spermidine:putrescine 4-aminobutyltransferase (propane-1,3-diamine-forming)

spermidine + putrescine = sym-homospermidine + propane-1,3-diamine [RN:R01919]

R01919

spermidine [CPD:C00315];
putrescine [CPD:C00134]

The reaction of this enzyme occurs in three steps, with some of the intermediates presumably remaining enzyme-bound: (a) NAD+-dependent dehydrogenation of spermidine, (b) transfer of the 4-aminobutylidene group from dehydrospermidine to putrescine and (c) reduction of the imine intermediate to form homospermidine. This enzyme is more specific than EC 2.5.1.44, 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).

1

Bottcher, 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.

2  [PMID:10611289]

Ober D, Hartmann T.

Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase.

Proc. Natl. Acad. Sci. U. S. A. 96 (1999) 14777-82.

Senecio vulgaris

3

Ober, D., Harms, R. and Hartmann, T.

Cloning and expression of homospermidine synthase from Senecio vulgaris: a revision.

Phytochemistry 55 (2000) 311-316.