EFFECT OF AMMONIUM, GLUTAMINE, METHIONINE SULFOXIMINE AND AZASERINE ON ASPARAGINE SYNTHESIS IN SOYBEAN LEAVES

When [14C]aspartate was infiltrated into soybean leaves, it was converted to asparagine. This conversion was markedly stimulated (10-fold) when ammonium or glutamine was added as a nitrogen donor. Methionine sulfoximine, an inhibitor of glutamine synthetase, inhibited asparagine synthesis from aspartate in the presence of ammonium but not in the presence of glutamine. Azaserine, a glutamine analog, inhibited the ammonium stimulated asparagine synthesis but no apparent inhibition of the glutamine stimulated asparagine synthesis was observed. The latter was likely due to the high glutamine concentration overcoming the inhibition. The results are consistent with asparagine being synthesized from aspartate with glutamine as the nitrogen donor. © 1979.