Trypsin inhibitors actions/effects

Table II gives the results of residual trypsin inhibitor levels for the various soymilk preparations. The 90 and 120 sec microwave treatments were the most effective in inactivating the trypsin inhibitor complex while hot water treated and unheated samples showed the highest levels. It is not surprising to find that microwave processing is more efficient than hot water in suppressing trypsin inhibitor considering the rapid penetration of food material by microwaves and the susceptibility of protein action to small heat induced changes in tertiary structure. Hence, Collins and McCarty (12) found microwaves produced a more rapid destruction of endogenous potato enzymes (polyphenol oxidase and peroxidase) than hot water heating.

Another protein in soybeans that is destroyed by extrusion is the trypsin inhibitor, which is produced in the pancreas. Without the action of trypsin, the animal cannot use protein, as it is trypsin that splits or hydrolyzes the protein molecule. Other less important enzyme inhibitors that are denatured by the extruder relate to fats and the carbohydrate fraction of a diet. As the heat needed to deactivate enzymes is less than that needed to prepare oilseeds for oil extraction, the effect on the amino acids is much less severe, thus making them more available to the animal or higher in digestibility. 

The absorption-enhancing effects of protease inhibitors on the intestinal absorption of water-soluble compounds in rats was also examined. Some protease inhibitors may have absorption-enhancing activities in addition to their protease inhibitory actions (e.g., NaGC) [43, 44]. Aprotinin, bacitracin, and soybean trypsin inhibitor (STI) were used as protease inhibitors, while phenol red and fluorescein isothiocyanate (FITC)-labeled dextran with an average molecular weight of 4000 Da (FD-4) were selected as poorly absorbable and stable model compounds. Bacitracin enhanced the absorption of phenol red from the rat small and large intestine in the presence of the protease inhibitors, and similar results were noted for the intestinal absorption of FD-4 co-administered with bacitracin. Thus, bacitracin was seen to have not only a proteolytic inhibitory action but also an absorption-enhancing capability. 

The concept of a proteolytic mechanism in the production of inflammatory manifestations is supported by the demonstration of anti-inflammatory activity in various protease inhibitors, e.g. the trypsin inhibitors of the pancreas, soya bean, ovomucoid and potato . It is interesting to note that the inhibitor from potatoes exerts its effect even after the inflammation is well established , suggesting that protease action is a continuing feature of inflammation and not simply an initiating process. Various esterase inhibitors (dyflos, quinine, quinidine and chloroquine) also reduce capillary permeability induced by heat and the permeability globulins . 

At best, the evidence is indirect that cathepsins which toward peptides exhibit specificity patterns similar to those of known proteinases can, in fact, hydrolyze proteins. A satisfactory answer to this question must await the purification of the cathepsins to the degree of the extracellular proteinases. The main differences between the extracellular proteinases and cathepsins are as follows (1) The presence of a reducing agent is essential for the activity of cathepsins B and C but not for trypsin or chymotrypsin. (2) Crystalline tyrpsin inhibitor has no effect on cathepsin B. (3) The pH optima for cathepsins B and C lie between pH 3.5 and 6 compared to pH 8 to 9 favorable for the action of trypsin and chymotrypsin. 

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