Soy trypsin inhibitor

The investigation of the biological/functional activities of soy trypsin inhibitors showed unexpected results (Fig. 8). While BBI activity did not change during the enzymatic treatments, KTI activity was significantly reduced in the peptic hydrolysate and EPM product of soy albumin. 

SafePath Soy Residue Immunoassay Kit Not reported Not reported Not reported Soy trypsin inhibitor... 

Double-antibody (sandwich) ELISA using specific anti-soy trypsin inhibitor and other soy protein antibodies coated onto microwells... 

Trypsin Magnetic polyurethane-polystyrene beads with immobilized soy trypsin inhibitor [125]... 

Inactivation is determined by comparing ability of untreated PI versus pretreated proteinase inhibitor to inhibit bovine tr3rpsin hydrolysis of TAME in vitro for treatment all chemicals were used at 3.5 mM STI - soy trypsin inhibitor I POD - peroxidase ... 

Lupine seed, though used primarily in animal feeds (see Feeds AND FEED ADDITIVES), does have potential for use in human appHcations as a replacement for soy flour, and is reported to contain both trypsin inhibitors and hemagglutenins (17). The former are heat labile at 90°C for 8 minutes the latter seem much more stable to normal cooking temperatures. Various tropical root crops, including yam, cassava, and taro, are also known to contain both trypsin and chymotrypsin inhibitors, and certain varieties of sweet potatoes may also be impHcated (18). 

In order to produce soy protein, soybeans are first dehulled, flaked, and defatted to make white flakes . Soy protein concentrates are obtained by removing a portion of the carbohydrates from defatted and dehulled soybeans. Alcohol extraction is the method most commonly used to manufacture soy protein concentrates even though it results in the loss of isoflavones. Soy protein concentrates retain most of the fiber in the original soybean and must contain at least 65% protein on a moisture-free basis to meet quality standards. The most concentrated source of soy protein is soy protein isolates (or isolated soy protein, ISP), which is required to be at least 90% protein on a moisture-free basis. It is heat-treated during processing to insure inactivation of trypsin inhibitors. Most isolated soy protein is manufactured by water extraction from defatted and dehulled soybeans and it retains the natural isoflavones. 

RACKis J J, MCGEE J E, GUMBMANN M R and BOOTH A N (1979) Effects of soy proteins containing trypsin inhibitors in long term feeding studies in rats. J Am Oil Chem Soc. 56 (3) 162-8. 

Some legumes, including raw soy or peanut flour are known to contain certain antinutritional factors such as proteinase inhibitors and hemagglutinins or lectins (21,22). These factors can be inactivated, for the most part, by moist heat, during processing. Interestingly, peanut flour contained more trypsin inhibitor and lectin than did soy flour (22). 

Soy protein preparations contain a variety of biologically active compounds including saponins, fibers, trypsin inhibitors, and isoflavones (Potter, 2000). Hamsters and rats fed ethanol-extracted soy protein isolates had no ability to lower plasma cholesterol compared to intact soy protein isolates (Lucas et al., 2001 Ni et al., 1999). Extraction with ethanol is a treatment that would remove saponins, isoflavones, and other phytochemicals from the protein. Although one study showed that ethanol washing did not... 

In vitro IgE-binding studies performed with blood of patients suffering from soy allergy reported sensitivity to glycinin and Gly m 1 in over 90%, to Kunitz-trypsin inhibitor in 86%, and to prohlin (Gly m 3) in 69% of all investigated cases. A number of reactivities to other not yet completely characterized moieties between 5 and 20kDa have also been described (NDA Opinion 2004). 

Figure 1. Peptide maps of PVDF-bound soy bean trypsin inhibitor (190 pmol) digested with endoproteinase Glu-C in the presence of 50 pi of A) 1% RTX-IciO/lOO mM Tris pH, 8.0, B) 1% octylglucopyranoside/100 mM Tris pH, 8.0, and C) 1% heptylglucopyranoside/100 mM Tris, pH 8.0 as described in Materials and Methods. Digestion in the presence of 1% decylglucopyranoside was not analyzed by HPLC due to the presence of micelles.

An eight inch diameter expander, with 150 HP drive, can process preheated, cracked soybean at 60001bs/hr, producing full-fat soy with low levels of urease and trypsin inhibitor. Also, the hot product can pass into a screw-press (after its moisture is allowed to flash to 5-7%). As most of the oil cells have been ruptured by the expander, a screw-press can process the soybean at three times the capacity it would have had with unexpanded soybean. 

Considerable research has identified several potential health benefits associated with increased soy consumption, and soybeans, which contain trypsin inhibitors such as phytic acid, saponins, and phytoestrogens, are now looked upon for potential health benefits. 

Legume seeds contain a number of antinutritive components, mainly lectin and trypsin inhibitors. The efficiency of the nutritional utilization of diets containing soybean is well below that expected on the basis of chemical composition [196]. In order to reduce the extent of this constraint, at present, all soy products go through expensive heat treatment or other processing procedures that can lead to losses of essential amino acids and to the production of toxic by-products. It is hoped that an effective strategy will help improve the nutritional value of soy proteins [197,198]. 

The soy storage proteins (glycinin /3-conglycinin) and an antigenic soy protein (of low molecular mass) were degraded by the proteolytic process and an apparent loss of antigenicity was observed. However, the proteolytic effect on soy lectin and Kunitz trypsin inhibitor was obviously lost, although some minor decrease in immunoreactivity could be observed. 

Figure 8 Reaction of trypsin inhibitors and enzymatically modified soy albumin samples with trypsin after native PAGE. Samples run were (1) Kun-itz trypsin inhibitor (KTI) (2) a-chymotryptic hydrolysate of soy albumin (3) a-chymotryptic EPM of soy albumin (4) Bowman-Birk inhibitor (BBI) (5) peptic hydrolysate of soy albumin (6) peptic EPM of soy albumin (7) KTI (8) proteolytic hydrolysate of soy albumin (9) EPM product of soy albumin (10) BBI. The bands were visualized by exposure to trypsin and its substrate A-acetyl-DL-phenylalanine /3-naphthyl ester followed by negative staining with tetrazotized o -dianisidine-ZnCl2 complex.

The Bowman Birk trypsin inhibitor is the smaller trypsin inhibitor with MW -S.OkD and binding sites for trypsin and chymotrypsin (Birk, 1985). BBI is more heat-stable than the Kunitz inhibitor probably resulting from its great proportion of disulfide cross-linking at 7 per mole BBI. Although BBI is present in much lower amounts in raw soybeans, its relative heat stability may be the main reason for the residual STI activity in moist-heated soybean protein products. Friedman and Brandon (2001) reported about 7 pg/mL BBI in soy-based infant formula as measured by ELISA while Dipietro and Liener (1989) reported <0.1 pg/mg (their limit of detection by ELISA) for SIR... 

Gumermann, M.R. W.L. Spangler G.M. Dugan E.C. Baker J.J. Rakis. Pancreatic response in rats and mice to trypsin inhibitors from soy and potato after short- and long-term dietary exposure. /. Nutr. 1989,119, 1598-1609. 

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