Beneficial Effects of Bioactive Peptides Derived from Soybean on Human Health and Their Production by Genetic Engineering

Soybean [Glycine max (L.) Merrill] is one of the oldest cultivated crops of the Far East. For centuries, the Oriental people, including the Chinese, Japanese, Koreans, and Southeast Asians, have used soybean as a staple source of dietary protein and oil. It is one of the five commercial food crops, besides rice, wheat, barley, and millet. Soybean is very important for vegetarians and vegans because of its high protein content and abundance of vitamins, minerals, and fiber. Because of its versatility, it can be prepared into a variety of foods, including fermented and nonfermented foods. Asians consume about 20–80 g of traditional soy foods daily, the most common being tofu, miso, and tempeh (Fournier et al., 1998; Messina & Flickinger, 2002), whereas Americans consume only about 1–3 g daily (Cohen et al., 2000; Fournier et al., 1998), mostly in processed forms such as soy drinks, breakfast cereals, and energy bars. Soybean-based foods have generated much interest because of the evidence that consumption of large amounts of soybean can lower the risk of chronic diseases such as cardiovascular disease and cancer; this effect is particularly noticeable among Asian populations because of their high soy food intake (Kulling et al., 2001; Persky et al., 2002; Tikkanen & Adlercreutz, 2000). In addition, consumption of soy foods may reduce the risk of osteoporosis and help alleviate menopausal symptoms (Genovese & Lajolo, 2002; Messina, 2000; Persky et al., 2002), which are major health concerns for women. Soybean-based foods contain an array of biologically active compounds that can confer important health benefits such as antioxidant effects (Setchell, 1998; Tsai & Huang, 1999). These phytochemicals include saponins, phytates, protease inhibitors, phenolic acids, and lecithin, all known for their anticancer potential (Cohen et al., 2000; Messina & Flickinger, 2002); phytosterols, which have hypocholesterolemic effects; isoflavones, which are known for several health benefits (Fukui et al., 2002); and omega-3 fatty acids, which have wellrecognized cardioprotective effects. Among these compounds, isoflavones have attracted the most attention (Messina & Flickinger, 2002; Messina & Loprinzi, 2001). The proteins β-conglycinin (7S globulin) and glycinin (11S globulin) constitute up to 90% of the total soy protein (Gianazza et al., 2003). Evaluation of these dietary proteins is very interesting because their hydrolysis by proteases produces peptides with biological activities. A growing