Transgenic plants containing free amino acids, particularly at least one amino acid selected from among glutamic acid, asparagine, aspartic acid, serine, threonine, alanine and histidine accumulated in a large amount, in edible parts thereof, and a method of producing them are provided. In this method, glutamate dehydrogenase (GDH) gene is introduced into a plant together with a regulator sequence suitable for over expressing the sequence encoding GDH gene in plant cells.
 This invention was made with government support under grant no.:GM32877 awarded by the National Institute of Health, and grant nos.:DEFG0292 and ER20071 awarded by the Department of Energy. The government has certain rights in the invention.