ARS | Publication request: Inhibition of soybean seeds in warm water results in the release of copious amounts of Bowman-Birk protease inhibitor, a putative anticarcinogenic agent

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 28, 2012
Publication Date: February 28, 2012
Citation: Palavalli, M.H., Natarajan, S.S., Wang, T.T., Krishnan, H.B. 2012. Inhibition of soybean seeds in warm water results in the release of copious amounts of Bowman-Birk protease inhibitor, a putative anticarcinogenic agent. Journal of Agricultural and Food Chemistry. 60:3135-3143.

Interpretive Summary: Soybeans are a rich source of protein. Several studies have demonstrated that diets containing soybean protein contribute to human health beyond the nutritional aspects. Among soybean seed proteins, Bowman-Birk proteinase inhibitor (BBI) has received particular attention because this protein possesses chemopreventive activity against different types of cancer. BBI is traditionally purified by ammonium sulfate precipitation, organic solvent extraction, gel filtration, column chromatography, or high performance liquid chromatography. Each of these procedures is time-consuming and result in limited amounts of purified material. Therefore, establishing a simple protocol for the isolation and purification of these proteins would be beneficial. The results presented in this study show that soybean seeds release large amounts of BBI when incubated in warm water. The BBI released in the warm water inhibits the growth of MCF7 breast cancer cells. Our procedure can serve as a simplified alternative method for the preparation of BBI which is being used as a cancer chemoprotective agent.

Technical Abstract: Protease inhibitors play a protective role against pathogenic microorganisms and herbivorous insects. The two predominant protease inhibitors of soybean seeds are the Kunitz trypsin inhibitor (KTI) and Bowman-Birk protease inhibitor (BBI). In this study we report that soybean seeds incubated in warm water releases large amounts of proteins into the surrounding media. Two-D gel electrophoresis analysis of the seed exudates resulted in the separation of 93 distinct protein spots out of which 90 spots were identified by LC-MS/MS. The basic 7S globulin and the Bowman-Birk protease inhibitors are the two predominant proteins found in the soybean seed exudates. In addition to 7S and 11S seed storage proteins others known to protect the seeds against pathogens and pests including Kunitz trypsin inhibitor, peroxidase, a-galactosidase, and endo-1.3-ß-glucanase were also identified in the seed exudates. Soybean seed exudate obtained by incubating the seeds in warm water was also able to inhibit the growth of human breast cancer cell line MCF-7. Since soybean seeds release large amounts of enzymatically active BBI when immersed in warm water our procedure could be exploited as a simplified alternative method for the preparation of BBI concentrate which is being used as a cancer chemoprotective agent.