Stability of Red Kidney Bean Serine Protease Inhibitor to Heat and Pepsin Digestion

Document Type

Poster Session

Document Subtype


Presentation Date

Fall 11-16-2012

Conference Name

Indiana University Undergraduate Research Conference (IUURC)

Conference Location



Serine proteases are a class of enzymes involved in the digestion and processing of proteins. They play important roles in all aspects of life from the time of conception of an individual to his death. However, in order to properly function, their activity needs to be controlled. One of the mechanism by which living organisms control the activity of serine proteases is by synthesizing a variety of relatively specific protease inhibitors. Protease inhibitors form a non-covalent complex with the protease resulting in the temporary inactivation of the protease. Protease inhibitors have been frequently used in the investigation of the structure and mechanism of serine proteases as well as therapeutic agents in the diseases resulting from uncontrolled or unwanted activity of serine proteases.

Here, we report our preliminary results on the heat and pepsin stability of kidney bean serine protease inhibitors. The inhibitory activity was measured against chymotrypsin and trypsin by using synthetic chromogenic substrates. Our results show that kidney bean serine protease inhibitor is exceptionally stable to heat (up to 100oC) and to pepsin digestion. We have also analyzed the pepsin digested samples by polyacrylamide gel electrophoresis to compare the protein bands in the digested and the undigested samples. The results will be presented in the poster.

There are two possible fates of the inhibitor when red kidney beans are consumed. One, the inhibitor may be denatured by heat and destroyed by pepsin and thus can serve as a source of nutrition. Two, as our present studies suggest, it may be stable to heat treatment and pepsin digestion and thus can pass to small intestine undigested but active and can influence the process of digestion by inhibiting enzymes like chymotrypsin and trypsin. Our results support the second possibility.


Protease Inhibitors; Red Kidney Bean; Serine Proteases; Stability to Pepsin


Biochemistry, Biophysics, and Structural Biology

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