Stability of the allergenic soybean Kunitz trypsin inhibitor.
The soybean Kunitz trypsin inhibitor (SKTI) is a 21.5 kDa allergenic protein that belongs to the family of all antiparallel beta-sheet proteins that are highly resistant to thermal and chemical denaturation. Spectroscopic and biochemical techniques such as circular dichroism (CD), ANS fluorescence and proteolysis were used to study its molecular structure under denaturing conditions such as acid and heat to which these allergens are commonly exposed during food processing. Reduction of native SKTI leads to its complete and rapid proteolysis by pepsin in simulated gastric fluid (SGF). Limited proteolysis with chymotrypsin during renaturation after heating showed that the native structure reforms at around 60 degrees C reversing the denaturation. CD spectra revealed that under acid denaturing conditions, SKTI shows major changes in conformation, indicating the possibility of a molten structure. The existence of this intermediate was established by ANS fluorescence studies at different concentrations of HCl. The remarkable stability of SKTI to both thermal and acid denaturation may be important for its role as a food allergen.
Roychaudhuri
Robin
R
Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA.
Sarath
Gautam
G
Zeece
Michael
M
Markwell
John
J
D000485:Allergens / Q000737:chemistry*; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D002942:Circular Dichroism; D005750:Gastric Juice / Q000187:drug effects / Q000378:metabolism; D006358:Hot Temperature; D006851:Hydrochloric Acid / Q000494:pharmacology; D010434:Pepsin A / Q000378:metabolism; D011489:Protein Denaturation; D013025:Glycine max / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014357:Trypsin / Q000737:chemistry*; D014360:Trypsin Inhibitor, Kunitz Soybean / Q000737:chemistry* / Q000494:pharmacology
D000485:Allergens; D014360:Trypsin Inhibitor, Kunitz Soybean; D002918:Chymotrypsin; D014357:Trypsin; D010434:Pepsin A; D006851:Hydrochloric Acid