A new polyamine 4-aminobutylcadaverine. Occurrence and its biosynthesis in root nodules of adzuki bean plant Vigna angularis.

Root nodules of adzuki bean plant (Vigna angularis) contained a novel polyamine. The chemical structure of the new polyamine was determined to be NH2(CH2)5-NH(CH2)4NH2 (4-aminobutylcadaverine) based on gas chromatography-mass spectrometry. The occurrence of 4-aminobutylcadaverine was specific to the root nodules, since the unusual triamine was not detected in other organs of the adzuki bean plant. Bacteroids, isolated from root nodules, contained both sym-homospermidine and 4-aminobutylcadaverine, whereas the plant cytosol fraction contained large quantities of putrescine and cadaverine. A cell-free extract of bacteroids showed the ability to form this triamine from putrescine and cadaverine under the presence of NAD+ and K+. 1,3-Diaminopropane and NADH were inhibitory for the synthesis of both sym-homospermidine and 4-aminobutylcadaverine. [1,4-15N]Putrescine was incorporated not only into sym-homospermidine but also into 4-aminobutylcadaverine by the cell-free extract of bacteroids when incubated with excess cadaverine. Analysis of the fragment ion peaks in the 15N-enriched 4-aminobutylcadaverine indicated the transfer of a aminobutyl moiety to the amino terminus of cadaverine. These results suggest that, in adzuki bean, 4-aminobutylcadaverine is formed through the action of homospermidine synthase in nodule bacteroids under a cadaverine-rich environment.