The comparative effect of prolonged feeding with raw and heated soybean mean on the growth response, pancreatic enlargement and pancreatic enzymes of chicks.

Prolonged feeding of chicks with raw soybean meal as the main protein source in the diet resulted in growth inhibition, pancreas enlargement, and increased content of pancreatic proteolytic enzymes. The effect of feeding with raw soybean meal as compared to heated soybean meal upon total intestinal enzymatic activities in chicks was tested. The tendency of chicks to overcome the effects of raw soybean meal is expressed mainly by the increase of biosynthesis and secretion of proteolytic enzymes in the pancreas.

Enhanced urinary trypsin inhibitory activity in gentamicin-induced nephrotoxicity in rats.

We delineated in rats, the relationship between trypsin inhibitory activity in the urine and the nephrotoxic effects of gentamicin, eg, proteinuria and deterioration of glomerular filtration rate (GFR), measured by creatinine clearance. Gentamicin, 70 mg/kg per day, was injected intraperitoneally for 6-10 successive days. Serum and urine gentamicin levels were determined by a microbiological test. Trypsin inhibitory activity was assayed by the casein digestion method. The results showed a steady increase in urinary trypsin inhibitory activity starting from the fourth injection day. The increased levels of urinary trypsin inhibitory activity were associated with increased levels of urinary gentamicin excretion (r = 0.36, p less than 0.02, n = 50 after the fourth injection day), and were significantly higher than in control groups (p less than 0.001). The urinary trypsin inhibitory activity was inversely correlated with the GFR (r = -0.45, p less than 0.01, after the second injection day). The serum trypsin inhibitory activity remained unchanged throughout the study period in all groups. These data suggest that increased urinary trypsin inhibitory activity may be involved in the pathogenesis of gentamicin-induced nephrotoxicity.

Photoreactive, active derivatives of trypsin and chymotrypsin inhibitors from soybeans and chickpeas.

The photoreactive arylsufenyl chloride 2-nitro-4-azidophenylsulfenyl chloride (2,4-NAPS-Cl) has been used for the selective modification of tryptophan in Kunitz's soybean trypsin inhibitor (STI). The ultraviolet absorption spectrum and amino acid analysis of 2,4-NAPS-STI indicated that only one of the two tryptophans, 93 or 117, present in STI was modified. Amino acid analysis of the two separated CNBr-cleavage products of 2,4-NAPS-STI showed that only tryptophan 93 underwent modification. 2,4-NAPS-STI fully retained its inhibitory activity against trypsin. The covalent attachment of 2,4-NAPS-STI to tritiated trypsin after photolysis was demonstrated by exclusion chromatography on Sephadex G-50 in the presence of guanidine hydrochloride. Photoreactive derivatives of the Bowman-Birk trypsin-chymotrypsin inhibitor (BBI) from soybeans and of CI, the trypsin-chymotrypsin inhibitor from chick peas were prepared by selective modification of the epsilon-amino groups of 2,4(5)-NAPS-Cl. The ultraviolet absorption spectra of the photolabeled inhibitors indicated that three out of the five lysines of BBI and one of the seven lysines of CI were modified. The inhibitory activity of the modified inhibitors towards trypsin and chymotrypsin was not reduced even after photolysis. The specific lysine residues that constitute the trypsin-inhibitory sites of BBI and CI did not react with the photoreactive reagents. Further modification of the photoreactive derivatives of BBI and CI with maleic anhydride, directed towards the trypsin-reactive sites, resulted in almost complete loss of trypsin-inhibiting activity without reducing the ability to inhibit chymotrypsin. A pronounced potentiation effect (approximately 2x) of the chymotrypsin inhibiting activity was noted for 2,5-NAPS-CI and it was retained even after maleylation followed by photolysis, raising the possibility of exposure of an additional chymotrypsin inhibitory site in CI.

Protein proteinase inhibitors in legume seeds--overview.

Protein proteinase inhibitors are widely distributed in plant seeds, particularly in legumes. The specificity and potency of inhibition depend on defined inhibitory sites and on the animal species of the target proteinase. Feeding experiments on diets containing isolated soybean trypsin inhibitors (the Kunitz soybean trypsin inhibitor STI and the Bowman-Birk trypsinchymotrypsin inhibitor BBI) caused insignificant growth depression in rats and chicks, but induced enlargement of the pancreas in rats, chicks and mice but not in pigs, dogs, calves, monkeys and presumably humans. The trypsin-inhibitory site has been responsible for induction of the pancreatic enlargement. The trypsin-chymotrypsin inhibitors from soybeans and from chickpeas inhibit insect midgut proteinases, supporting the hypothesis that proteinase inhibitors comprise a built-in defense mechanism of the seed against insects. Findings on the involvement of proteinase inhibitors, such as BBI, in prevention of tumorigenesis suggest a possible positive contribution of the inhibitors to the nutritional value of legume seeds. BBI is also an effective inhibitor of nephrotoxicity induced by the antibiotic gentamicin. BBI does not cause side effects and does affect the antimicrobial activity. The in vitro effects of proteinase inhibitors on animals should be interpreted with caution when related to humans.