Biochemistry and Molecular Biology of Soybean Seed Storage Proteins

Abstract

Soybean (Glycine max[L.] Merr.) is one of the principle field crops grown in the United States. From a crop with no significant economic value at the turn of this century, soybeans have made remarkable strides in U.S. agriculture, claiming the stature of the number two U.S. cash crop. Soybean is an important source of edible vegetable oil and protein throughout the world and is used in a multitude of food and industrial applications. Even though soybeans are a rich source of protein for livestock and humans, the nutritional quality of soybean proteins is not optimal. Some of the problems associated with soybean proteins include (1) presence of anti-nutritional factors such as trypsin inhibitor, (2) undesirable beany flavor, (3) elicitation of allergic reactions in susceptible individuals, (4) poor digestibility of soybean proteins, and (5) deficiency in sulfur-containing amino acids. As a consequence, concerted efforts are underway to improve the overall nutritive value of soybean proteins by both classical plant breeding and molecular biological approaches. This review article summarizes the current knowledge on the biochemistry and molecular biology of soybean seed storage proteins. Recent advances in the genetic improvement of amino acid composition of seed storage proteins are highlighted. The review also includes some recent achievements in modifying soybean seed composition.