Occurrence of L-2,4-diaminobutyrate decarboxylase activity in Acinetobacter.

Three strains of the genus Acinetobacter grown in a polyamine-free synthetic medium contained very high amounts of 1,3-diaminopropane, and there were also high concentrations in the extracellular growth medium. Little, if any, of the usual polyamines, putrescine, spermidine and spermine were found. There was no detectable activity of aminopropyltransferase (greater than 0.2 nmol spermidine formed/mg protein/h), which would be responsible for the formation of spermidine or spermine, expected precursors of 1,3-diaminopropane. These observations suggested the possibility of another mode of 1,3-diaminopropane biogenesis. Decarboxylation activity towards L-2,4-diaminobutyrate leading to the formation of 1,3-diaminopropane was detected in extracts of all three strains examined. The decarboxylase was partially purified from A. calcoaceticus ATCC 23055. The enzyme was active against only L-2,4-diaminobutyrate among the diamino acids tested and required pyridoxal phosphate as a cofactor. Mg2+ activated the enzyme.