Studies on soybean trypsin inhibitors. 2. Amino-acid sequence around the reactive site of soybean trypsin inhibitor (Kunitz).
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Ten susceptible x resistant and resistant x resistant crosses were made among eight varieties, of which seven were previously identified as resistant to one to four SMV strains, in order to investigate the inheritance of resistance to the four strains (Sa, Sc, Sg, and Sh) and the linkage relationship among the resistant genes. Seeds from F2 individual plants were randomly divided and planted in two separated nurseries, in which the seedlings were inoculated with two different strains. The genotype of each F2 plant was detected from the reaction of its F3 progenies to the two strains. The results showed that the resistance to each of the four strains was conditioned by a dominant gene which was labelled here with Ra, Rc, Rg, and Rh, respectively. All the four loci appeared to be in a same linkage group with the order of Rg--Rh--Ra--Rc. The recombination value between Ra and Rc was estimated to be 25.4 +/- 7.7%, and those between Rg and Rh, Ra and Rh, Ra and Rg, and Rc and Rg to be 27.3 +/- 5.4%, 23.5 +/- 5.2%, 41.1 +/- 8.5%, and 46.5 +/- 7.5%, respectively. The genes resistance to Sa in Kwanggyo and "7222" were determined at the same locus, so were the resistant genes for Sc. In addition, this linkage group seemed to be not related with the first and eighth linkage group.
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A 4 x 5 Youden square design was used to determine the effect of roasting temperature of whole soybeans on escape of CP from the rumen and disappearance of N from the small intestine in steers. Four steers (average BW 373 kg +/- 30.7) cannulated at the rumen, duodenum, and ileum were fed each of five diets (1.8% of BW) over five periods. The basal diet contained corn silage (50% of diet DM), alfalfa hay (24%), corn-urea premix (6%), corn starch grits (16.6%), and soybean oil (3.4%). Soybeans (16% of diet DM), either raw or heated to an exit temperature of 141, 149, or 157 degrees C in a commercial roaster, replaced the soybean oil and most of the corn starch grits in the soybean-containing diets. Ruminal ammonia N was lower (P < .05) for the basal diet than for the soybean-containing diets. Roasting temperature of whole soybeans had no significant impact on ruminal ammonia N. Total N reaching the duodenum was greater (P < .05) for steers fed the soybean diets than for steers fed the basal diet. Non-bacterial N (dietary N) at the duodenum was increased (P < .05) by feeding soybeans. Soybean N reaching the duodenum decreased with increased roasting temperature. Increased roasting temperature of whole soybeans seemed to make the soybeans more brittle, subsequently increasing degradation of CP in the rumen. However, disappearance of soybean N in the small intestine, as a proportion of the soybean N entering the small intestine, increased with increased roasting temperature. Apparent total tract N digestibility was increased (P < .05) by feeding soybeans. Flow to the duodenum and small intestinal digestibility of total, essential, and nonessential amino acids increased (P < .05) when soybeans were fed and when roasted vs raw soybeans were fed. Under normal roasting conditions, it seemed that little potential for heat damage to the soybean protein existed. Instead, undesirable effects of heating on handling characteristics of the soybeans were reached before the point at which loss of nutritive value occurred. Feeding steers diets containing roasted whole soybeans increased the N and amino acids available to steers over steers fed diets containing raw soybeans due to increased ruminal soybean nitrogen escape and increased small intestinal digestibility.
This study evaluated the nutritional value of raw lectin-free soybeans in comparison with raw Kunitz trypsin inhibitor-free soybeans, raw conventional soybeans, and commercial heat processed soybean meal (SBM). Analyzed lectin values (milligrams per kilogram) were 7.2, 7.1, and < 0.00015 for the Kunitz-free, conventional, and lectin-free soybeans, respectively. Three experiments were conducted using New Hampshire x Columbian male chicks fed 23% CP dextrose-soybean diets from 8 to 17 d of age. Growth performance of chicks fed lectin-free soybeans was greater (P < 0.05) than that of chicks fed raw conventional soybeans in all three experiments. However, performance of chicks fed lectin-free soybeans was lower than that of chicks fed Kunitz-free soybeans or SBM. The SBM yielded weight gains and feed efficiencies that were much higher than those observed from any of the raw soybeans. True amino acid digestibility and TMEn of the lectin-free and conventional soybeans were determined using the precision-fed cecectomized rooster assay. Seven roosters were crop-intubated with 30 g of soybeans and excreta were collected for 48 h. Digestibility coefficients of most amino acids for lectin-free soybeans were 5 to 8 percentage units higher than those for conventional soybeans, but the differences were not significant (P > 0.05). Likewise, the TMEn for lectin-free soybeans was 11% higher than that for raw conventional soybeans (3.577 vs 3.227 kcal/g DM) but the difference was not significant (P > 0.05). The results of this study indicate that the nutritional value of raw lectin-free soybeans is greater than raw conventional soybeans but is less than raw Kunitz-free soybeans and SBM, suggesting that trypsin inhibitor is a greater antinutritional factor than lectins.
Soybean consumption may be beneficial to prevention of certain human cancers. Low incidence of colon cancer in Asian countries is associated with consumption of soybean products. A limited number of human and animal studies suggested that soybean consumption might prevent colon cancer; other studies did not support this conclusion. Therefore, it is important to understand the biological effects of soybeans on colon cells. In the present study, cultures of Caco-2, SW620, and HT-29 cells were treated with soybean extract, the soluble fraction of a soybean product. The crude extract contains proteins and many soluble components of soybeans. After incubation with soybean extract (1-6%, vol/vol) for 24 h, most Caco-2 cells were found to contain numerous vacuoles within the cytoplasm and to become very flat. Exposure to > 6% soybean extract resulted in cell death and giant vacuoles. Soybean extract (0.25-2%) induced small vacuoles within the cytoplasm of SW620 cells. SW620 cells detached from culture dishes at > 2% soybean extract. Exposure to 0.5-2% soybean extract produced vacuoles within HT-29 cells similar to those observed in SW620 cells. Soybean extract significantly reduced density of Caco-2, SW620, and HT-29 cells. Reducing protein content of soybean extract reduced but did not abolish its effects on colon cells. Purified genistein (12.5 micrograms/ml) was capable of producing morphological changes similar to those observed after treatment of colon cells with soybean extract. Assays using annexin V-propidium iodide demonstrated that treatment of Caco-2 and SW620 cells with soybean extract increased cell death. Membranes of vacuoles in soybean-treated Caco-2 and SW620 cells were labeled with Texas red-conjugated wheat germ agglutinin, a cytological marker for the Golgi apparatus. Exposure to soybean extract enhanced protein levels of Rab6, a small GTP-binding protein that is involved in regulation of membrane traffic of the Golgi apparatus. Data from this study suggest that exposure to soybean extract or isoflavones affects morphology and survival of colon cancer cells and that the response to soybean extract varies depending on the cell lines examined.
Twenty Holstein cows in midlactation were used in a Latin square design to evaluate the nutritional quality of a high protein soybean (CP 45%) fed raw or roasted. Treatments were 1) control (soybean meal); 2) conventional soybean (Maple Isle), raw; 3) conventional soybean, roasted; 4) high protein soybean (AC Proteus), raw; and 5) high protein soybean, roasted. Diets were formulated to be isonitrogenous and consisted of approximately 10% whole crop barley silage, 15% corn silage, 19% alfalfa silage, 31% rolled barley, 17% cracked corn, and from 6.5 to 8.6% of the appropriate protein source on a DM basis. Replacement of conventional soybean with the high protein soybean increased milk and milk component yields. All soybean treatments lowered milk protein percentages versus soybean meal although milk protein yield was only reduced for the raw Maple Isle soybean treatment. Milk fat percentage was reduced for the roasted AC Proteus soybean treatment versus soybean meal and both Maple Isle soybean treatments, although total milk fat yield did not differ among treatments. Heat treatment by roasting tended to affect total milk yield positively for both types of soybeans, but only the increase for Maple Isle was significant. Milk from cows fed full fat soybeans had more long-chain fatty acids than milk from cows fed soybean meal. Roasting the soybeans further increased the amounts of long-chain fatty acids. The new high protein soybean, AC Proteus, appears to be an excellent source of supplemental protein and energy for lactating dairy cows.
An experiment was conducted with ileally cannulated pigs to determine the apparent digestibility of amino acids and N in raw or heated conventional or low-trypsin-inhibitor soybeans. Six littermate barrows initially averaging 24 kg were fed cornstarch-based diets (10.5% CP, .68% lysine, 3,558 kcal of ME/kg) supplemented with raw (unheated), conventional soybeans; raw, low-trypsin-inhibitor soybeans; heated, conventional soybeans; heated, low-trypsin-inhibitor soybeans; or solvent-extracted soybean meal. Heating was achieved by autoclaving soybeans (after grinding) for 20 min at 110 degrees C. The urease activities of the two raw soybean sources were similar, but the trypsin inhibitor activity of the raw, low-trypsin-inhibitor soybeans was about one-half that of the raw, conventional soybeans. The lower trypsin inhibitor activity of the raw, low-trypsin-inhibitor soybeans was associated with an improvement in the apparent digestibility of amino acids and N compared with the raw, conventional soybeans (P less than .05). Heating reduced the urease and trypsin inhibitor activities and improved (P less than .05) the apparent digestibility of amino acids and N in both types of soybeans. However, the heated, conventional soybeans contained more trypsin inhibitor activity than the heated, low-trypsin-inhibitor soybeans and the digestibilities of the amino acids were lower (P less than .05). Although the urease and trypsin inhibitor activities of the two heated soybean sources were similar to or less than those of soybean meal, the digestibilities of amino acids were not as great (P less than .05) in the heated soybeans as in soybean meal.(ABSTRACT TRUNCATED AT 250 WORDS)
Fifteen cows were used in an experiment with a 5 x 5 replicated Latin square design to quantify the effect of particle size of roasted soybeans on milk production and fecal excretion of soybeans. The five experimental periods were each 2 wk long. Diets contained (percentage of dry matter) 33% alfalfa silage, 17% corn silage, 30.6% high moisture ear corn, 18% soybeans, and 1.4% mineral supplement. The five dietary treatments included raw whole soybeans or roasted soybeans in four particle sizes (whole and half, half and quarter, quarter and smaller, and coarsely ground). Mean particle sizes of the raw soybeans and of the roasted soybeans in whole and half sizes were > 4.75 mm. Mean particle sizes of the roasted soybeans in half and quarter, quarter and smaller, and coarsely ground roasted soybeans were 2.92, 2.01, and 1.59, respectively. During the normal handling of roasted soybeans, a large number of seeds was broken into halves in the treatment with whole and half sizes (36%, wt/wt basis). Production of 3.5% fat-corrected milk was 35.4, 37.7, 37.2, 35.1, and 35.4 kg/d for cows fed raw soybeans; roasted soybeans in whole and half, half and quarter, and quarter and smaller sizes; and ground roasted soybeans, respectively. Cows that were fed raw soybeans excreted the largest amount of visible soybean particles in feces, and cows that were fed ground roasted soybeans had the least amount of soybeans in the feces (61.3 vs. 10.6 g of soybeans/kg of fecal dry matter). Roasted soybeans in half and quarter sizes are optimal for milk production.
Most traits introduced into genetically engineered crops result from the expression of new proteins. As the first step toward assessing the allergenic potential of genetically modified organism (GMO) food, immunologic and physicochemical characterizations are needed. We prepared crude extract from GMO soybeans, wild soybeans, curd, and soy milk and then performed sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). After acidification with HCl, the samples were separated to globulin and whey. To evaluate changes in protein composition, either the samples were heated or pepsin was added. Polymerase chain reaction with primer encoding the 35S-promotor and the 3-enol-pyruvyl-shikimat-5-phosphat-synthase gene were performed, respectively, to detect the GMO component. SDS-PAGE results showed definite protein bands at 80 kDa in GMO soybean, 50 kDa in wild soybean, and a similar distribution of protein bands was noticed below 40 kDa. It was difficult to observe protein distribution because of modifications that occurred during processing in soybean-processed products. After heating, proteins of GMO and wild soybeans showed similar distributions and no distinct bands were detected at 50 and 80 kDa. Although SDS-PAGE analyses of raw GMO and wild soybeans differed, the same protein bands of 68, 37, and 20 kDa were observed in the globulin fraction after acidification. After adding pepsin, 20- and 68-kDa bands were found preserved in GMO and wild soybeans. The polymerase chain reaction procedures with primers specific to GMO soybeans showed that GMO soybeans and some curd samples included a GMO component. The skin test results of 49 patients showed 13 positive results to wild soybeans and 8 positive results to GMO soybeans. One patient had a positive skin test result to GMO soybeans only. Sera from nine patients with positive skin tests to the crude extract and a positive capsulated allergen product test to the soybean antigen were used for the immunoblotting of GMO and wild soybeans. GMO soybeans revealed a unique strong immunoglobulin E binding band at 25 kDa in some patients and wild soybeans showed a strong immunoglobulin E binding band at 30-36 kDa. To assess the allergenicity of GMO food, more research, including a selection of controlled sample materials and immunoassays of qualified sera, is needed.
In trial 1, eight Holstein heifers weighing 410 kg were used in an 8 x 8 Latin square and fed TMR containing 79.3% alfalfa silage and 20% soybeans. The first four treatments were raw soybeans, soybeans roasted and held for 3 h at the roasting temperature, extruded soybeans, and soybeans roasted in a California Pellet Mill Jet-Sploder. The remaining four treatments were obtained by altering the residence time of soybeans in the Jet Sploder. The temperatures of soybeans exiting the roaster were 117, 126, 138, and 154 degrees C for the last four treatments. The soybeans held 3 h postroasting and the extruded soybeans resulted in the highest estimate of postruminal available lysine. Blood plasma concentrations of essential and branched-chain AA were highest in heifers fed soybeans held 3 h postroasting. In trial 2, 44 Holstein heifers weighing 150 to 250 kg were assigned randomly to one of four TMR. Diets consisted of 91.8% alfalfa silage and 7.5% of one of four soybean treatments. Treatments were raw soybeans, soybeans roasted in a drum roaster with an exit temperature of 146 degrees C, and those roasted with exit temperatures of 141 or 146 degrees C and held for .5 h. Estimated postruminal available lysine was higher for soybeans roasted and held versus roasted or raw soybeans. However, BW gain for heifers was similar across diets, averaging .90 kg/d for 12 wk. Concentrations of AA in plasma were not affected by diet. Overall, results support the recommendation of holding soybeans for at least .5 h following roasting.