Abstract: Threonine is an essential amino acid for humans and in the animal feed industry where its levels in feed rations can significantly impact the cost of production of important meat sources, such as swine and poultry. Threonine as well as essential amino acids lysine and methionine are all synthesized via the aspartate family pathway. Aspartate kinase (AK) is the first enzyme in the pathway, and catalyzes the ATP-dependent phosphorylation of aspartate to form ?-aspartyl phosphate. AK constitutes the main regulatory step controlling the metabolic flux through the pathway, and is subject to end product inhibition by Lys and/or Thr. The current invention provides a method to produce a transgenic high free threonine soybean via the overexpression of feed-back-resistant AK enzymes in developing soybean plants and seeds. These modifications provide a method to enhance both plant nitrogen metabolism and crop growth performance.