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Identification of a new soybean Kunitz Trypsin Inhibitor mutation and its effect on Bowman-Birk protease inhibitor content in soybean seed

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Soybean seeds possess anti-nutritional compounds which inactivate digestive proteases, principally corresponding to two families: Kunitz Trypsin Inhibitors (KTi) and Bowman-Birk Inhibitors (BBI). High levels of raw soybeans/soybean meal in feed mixtures can cause poor weight gain and pancreatic abnormalities via inactivation of trypsin/chymotrypsin enzymes. Soybean protein meal is routinely heat treated to inactivate inhibitors, a practice which is energy intensive, costly and can degrade certain essential amino acids. In this work, we identified a new soybean germplasm accession which has reduced Kunitz trypsin inhibitor activity due to mutations affecting an isoform annotated as non-functional (KTi1), which was synergistic with a previously identified mutation (KTi3-); seeds homozygous for both mutations lack any detectable KTi protein. We observed significant proteome rebalancing in all KTi mutant lines, resulting in dramatically increased BBI protein levels. However, the overexpressed BBI isoforms are likely non-functional, as chymotrypsin inhibition declined in all KTi mutant lines.
Jason D. Gillman , Won-Seok Kim , Hari B. Krishnan
USDA Scientist Submission
Journal of agricultural and food chemistry 2015 Feb. 11 v.63 no.5
American Chemical Society
Journal Articles, USDA Authors, Peer-Reviewed
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