Compositions and methods for increasing the level of one or more selected free .epsilon. and/or .alpha.-N-acetylated amino acids in a selected tissue or organ of a plant are provided. In specific embodiments, the plant, plant part, seed or grain comprises a free .alpha.-N-acetylated amino acid content of at least 200 ppm or a ratio of free .alpha.-N-acetylated amino acid content to free non-.alpha.-N-acetylated amino acid content of about 3 to about 1000. Compositions comprising plants, plant parts, seed and grain having stably incorporated into their genome a heterologous polynucleotide encoding an amino acid-N-acetyltransferase polypeptide operably linked to a promoter active in the seed are provided. Further provided are compositions comprising a plant, plant part, seed or grain having stably incorporated into their genome a first heterologous polynucleotide encoding a first amino acid-N-acetyltransferase polypeptide operably linked to a first promoter active in the seed and a second heterologous polynucleotide encoding a second amino acid-N-acetyltransferase polypeptide operably linked to a second promoter active in the seed, wherein the first and the second amino acid-N-acetyltransferase polypeptide acetylate the .alpha.-amine of distinct amino acids. Compositions comprising food sources, feed and supplements, along with methods of increasing the nutritional value of a plant, plant part, seed or grain, are further provided.