Stability of the allergenic soybean Kunitz trypsin inhibitor

Abstract

The soybean Kunitz trypsin inhibitor (SKTI) is a 21.5 kDa allergenic protein that belongs to the family of all antiparallel h-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 jC 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. D

Stability of Murraya koenigii miraculin-like protein in different physicochemical conditions

“…Unlike most Soybean Kunitz-type inhibitors which exhibit a high degree of structural and functional stabilities at a range of temperatures and pH (Sweet et al, 1974;Onesti et al, 1991;Roychaudhuri et al, 2003Roychaudhuri et al, , 2004Azarkan et al, 2006), MKMLP showed unusual stability properties. It possesses a compact structure which is retained at high temperature but functional stability is lost.…”

“…Among them, Kunitz soybean trypsin inhibitors are proteins with molecular mass of about 20 kDa. The stability studies have shown that most Kunitztype inhibitors are highly stable over a broad range of pH and temperature with a remarkably resistance to proteolytic degradation (Sweet et al, 1974;Onesti et al, 1991;Roychaudhuri et al, 2003Roychaudhuri et al, , 2004Azarkan et al, 2006). It has been reported that a Bowman-Birk inhibitor is involved in the tolerance of salt stress in wheat (Shan et al, 2008).…”

Processing Foods without Soybean Ingredients

“…Soybean KTI is classifi ed in the family of antiparallel β -sheet proteins that are highly resistant to chemical and thermal denaturation [73] . Moroz and Yang [74] demonstrated that the serum of a patient with an occupational respiratory disorder had IgE antibodies specifi c for soybean KTI (21 kDa).…”

Large‐Scale Identification of Intrinsically Disordered Proteins

“…Interestingly, because of the infl uence of anions on A state stability, not all acids are capable of quantitatively precipitating such proteins (58) . Note also that some structured proteins adopt nonsticky A states and thus remain in solution (55) . Finally, some ordered proteins might be exceptionally stable and simply remain folded and soluble even at extremely low pH (57,61) .…”