Chemical inactivation of soybean trypsin inhibitors

Abstract

Sodium metabisulfite and glutaraldehyde were used alone and in combination to inactive Kunitz trypsin inhibitor (TI) in model systems and TI in lyophilized alkaline soy meal extract. Reaction of glutaraldehyde (0.1 to 3.0%, based on total volume of the reaction mixture) with Kunitz TI (3 mg/ml buffer) at 25 C resulted in 60-75% reduction in activity. Treatment of soy meal extract containing 0.08 mg TI/mg at a concentration of 10 mg sample/ml buffer under similar reaction conditions reduced TI activity only 40%, however. A reaction temperature of 75 C had little additional effect on TI inactivation. On the other hand, sodium metabisulfite (0.05 to 1.0 raM) inactivated >96% Kunitz TI within 1 hr at 75 C and 75-94% of the TI in soy meal extract. The combination of 0.6 mM metabisulfite and 0.5% glutaraldehyde at 75 C inactivated >99% Kunitz TI, and combination of 0.6 mM metabisulfite and up to 3% glutaraldehyde inactivated 88% of TI in soy meal extract vs 91% inactivation with metabisulfite alone. Thus, metabisulrite plus glutaraldehyde inactivated Kunitz TI better than either one alone, while bisulfite alone best inactivated TI in soy meal extract. When the reactions were performed at neutral pH, protein solubility of 80% or better was retained.

Purification and characterization of trypsin inhibitor from Cicer arietinum L. and its efficacy against Helicoverpa armigera

“…Therefore, in all the subsequent experiments, 50 mM phosphate buffer (pH 7.6) was used for extraction. Previously, different media have been reported to be suitable for extraction of trypsin inhibitor by various workers (Sessa and Nelsen, 1991;Domoney et al, 1993;Marconi et al, 1993;Hajela et al, 1999;Maggo et al, 1999).…”

Chemical inactivation of soybean protease inhibitors

“…Trypsin, % residual active inhibitor = 60.126 (+_ 1.441} -0.7757 (_+ 0.0317} X It(me in min), R 2 ---0.99 [12] Chymotrypsin, % residual active inhibitor = 60.800 (+ 3.671} -0.6147 (+_ 0.0894) x (time in rain), R 2 = 0.96 [13] When the slopes were compared by t-test, the trypsin, % residual active inhibitor had a tendency (P --.09) to decline at a faster rate than the chymotrypsin residual. With time, temperature and reagent concentration as variables, we found that treatments of KTI and BBI with 0.6 mM Na2S~Os, 10 mM AH + 0.8 mM CuSO4 or 20 mM H202 + 0.8 mM CuSO4 for 0.5-1 hr at 65-90~ inactivated 40 to more than 85% of both inhibitors.…”

Effect of salts on soy storage proteins defatted with supercritical CO2 and alcohols

“…These data show that Na 2 SO 4 steep treatment provides no significant difference in NSI values when compared with water-steeped cracked beans, whereas the Na 2 SO 3 -steeped beans exhibited a significantly higher NSI than did the other two treatments (comparisons are based on the following slopes and intercepts, calculated from the data in Figure 3, where H 2 O vs. SO 3 2− , slope < 0.01, intercept < 0.01; H 2 O vs. SO 4 2− , slope 0.11, intercept 0.12; SO 3 2− vs.…”

“…Protein solubility results from the balance of the attraction of protein molecules for each other and the solvent molecules for the solute (27). The reducing salt Na 2 SO 3 will cleave disulfide bonds with introduction of a negatively charged sulfonate group: PS-SP + SO 3 2− ⇒ PS-SO 3 − + PS − where P = protein (20).…”

“…Sessa and Nelsen (2) also demonstrated that reducing salts, particularly sodium sulfite, proved to effectively heat-stabilize the β-conglycinin (7S) and glycinin (11S) storage proteins in salt-steeped cracked beans. Sulfiting agents were used to inactivate soybean protease inhibitors (3)(4)(5) as well as to preserve the nitrogen solubility index (NSI) during defatting of salt-steeped beans with either n-hexane or supercritical CO 2 (SC-CO 2 ) (4). However, these authors (4) did not assess changes in NSI that may have occurred as a result of a lengthy steep treatment.…”