Novel and simple method to determine contents of Kunitz trypsin inhibitor and Bowman-Birk inhibitor in soybeans

Authors: Liu, Keshun

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/26/2023
Publication Date: 6/19/2023
Citation: Liu, K. 2023. Novel and simple method to determine contents of Kunitz trypsin inhibitor and Bowman-Birk inhibitor in soybeans. Meeting Abstract. Day 1, B1 Session, 6/19/23. Available. https://www.wsrc11vienna.com/.

Interpretive Summary:

Technical Abstract: Soybeans are the number one source of plant proteins for food and feed, but the natural presence of proteinase inhibitors (PI), namely Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitors (BBI), can induce undesirable or desirable health effects. Since both inhibitors have inhibition toward trypsin, measurement of trypsin inhibitor activity cannot differentiate them. Over the years, three major types of methods have been developed to measure KTI or BBI concentration in soy products, including gel electrophoresis, immunoassays, and chromatography. However, these methods suffer from several inherent problems, including complex procedures, requirements of specific and expensive instruments, limitation to only KTI or BBI, time- and labor-intensity, inaccuracy, and high cost. They are more suitable for qualitative than quantitative measurements. For the past few years, we have developed and optimized methods to accurately measure trypsin inhibitor activity and chymotrypsin inhibitor activity, respectively. Using the two new methods as a basis, we have recently developed a simple and cost-effective method to simultaneously determine contents of KTI and BBI in soybeans. We validated the new method by measuring two KTI-null and two wildtype (common) soybean cultivars for PI composition. On average, wildtype soybeans contained 14.8 mg/g KTI and 6.2 mg/g BBI, totaling 21 mg/g, but KTI-null soybeans had about half amounts of total PI, resulting from several-fold reduction in KTI content. By developing the novel and simple method that can differentiate the two inhibitors in terms of mass composition, we can easily identify which inhibitor has more effect on animal nutrition and human health, and at the same time facilitate plant scientists to screen and develop soybeans with altered PI composition. All these efforts will lead to the development of better soybeans for improved feed or food with optimal nutrition.