Natural abundance of 15N in amino acids and polyamines from leguminous nodules:: unique 15N enrichment in homospermidine

The natural N-15 abundance (delta(15)N value) in acetylpropyl derivatives of amino acids and in ethyloxycarbonyl derivatives of polyamines was determined using a gas chromatography/combustion/mass spectrometer (GC/C/MS). delta(15)N values determined for 12 amino acids and five polyamines by GC/C/MS were identical to those obtained by a direct combustion method using an automatic nitrogen and carbon analysis (AMCA) mass spectrometer, the difference being less than +/-1.0% in most cases, The GC/C/MS method was used to analyse delta(15)N values in the amino acids and polyamines from root nodules of pea and faba bean and from stem nodules of Sesbania rostrata, The analysis of delta(15)N values revealed that homospermidine had high delta(15)N values, as much as +40 parts per thousand, while the amino acids investigated had delta(15)N values between -3 and +6 parts per thousand, putrescine between +2 and +8 parts per thousand, cadaverine between fl and +7 parts per thousand, spermidine between -2 and +4 parts per thousand, and spermine between 0 and +6 parts per thousand, The mechanism of N-15 enrichment in homospermidine is discussed.