N-acetylglutamate and N-acetylaspartate in soybeans (Glycine max L.), maize (Zea mays L.), [corrected] and other foodstuffs.

N-Acetylglutamate (NAG) and N-acetylaspartate (NAA) are amino acid derivatives with reported activities in a number of biological processes. However, there is no published information on the presence of either substance in foodstuffs. We developed a method for extracting and quantifying NAG and NAA from soybean seeds and maize grain using ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). The lower limit of quantification for both NAG and NAA was 1 ng/mL. The method was then utilized to quantify NAG and NAA in other foodstuffs (fruits, vegetables, meats, grains, milk, coffee, tea, cocoa, and others). Both NAG and NAA were present in all of the materials analyzed. The highest concentration of NAG was found in cocoa powder. The highest concentration of NAA was found in roasted coffee beans. Both NAG and NAA were found at quantifiable concentrations in all foods tested indicating that these two acetylated amino acids are common components of the human diet.

Metabolic engineering to increase isoflavone biosynthesis in soybean seed.

Isoflavone levels in Glycine max (soybean) were increased via metabolic engineering of the complex phenylpropanoid biosynthetic pathway. Phenylpropanoid pathway genes were activated by expression of the maize C1 and R transcription factors in soybean seed, which decreased genistein and increased the daidzein levels with a small overall increase in total isoflavone levels. Cosuppression of flavanone 3-hydroxylase to block the anthocyanin branch of the pathway, in conjunction with C1/R expression, resulted in higher levels of isoflavones. The combination of transcription factor-driven gene activation and suppression of a competing pathway provided a successful means of enhancing accumulation of isoflavones in soybean seed.