Antinutritives are compounds that interfere with the use of essential nutrients. They are generally divided into three classes: A, B, and C.
Type A antinutritives are substances primarily interfering with the digestion of proteins or the absorption and utilization of amino acids. They are also known as antiproteins. Strict vegetarians, for example, are in danger of nutritional inadequacy by this type of antinutritive. The most important type A antinutritives are protease inhibitors and lectins.
Protease inhibitors, occurring in many plant and animal tissues, are proteins that inhibit proteolytic enzymes by binding to the active sites of the enzymes. Proteolytic enzyme inhibitors were first found in avian eggs around the turn of the century. They were later identified as ovomucoid and ovoinhibitor, both of which inactivate trypsin. Chymotrypsin inhibitors also are found in avian egg whites. Other sources of trypsin or chymotrypsin inhibitors are soybeans and other legumes and pulses, vegetables, milk and colostrum, wheat and other cereal grains, guar gum, and white and sweet potatoes. The protease inhibitors of kidney beans, soybeans, and potatoes can additionally inhibit elastase, a pancreatic enzyme acting on elastin, an insoluble protein in meat. Animals, fed with food containing active inhibitors, show growth depression. This appears to be due to interference in trypsin and chymotrypsin activities and to excessive stimulation of the secretory exocrine pancreatic cells, which become hypertrophic. Valuable proteins may be lost to the feces in this case.
In vitro experiments with human proteolytic enzymes have been shown that trypsin inhibitors from bovine colostrum, lima beans, soybeans, kidney beans, and quail ovomucoid were active against human trypsin, whereas trypsin inhibitors originating from bovine and porcine pancreas, potatoes, chicken ovomucoid, and chicken ovoinhibitor were not. The soybean and lima bean trypsin inhibitors are also active against human chymotrypsin. Many protease inhibitors are heat labile, especially with moist heat. Relatively heat-resistant protease inhibitors include the antitryptic factor in milk, the alcohol-precipitable and nondialyzable trypsin inhibitor in alfalfa, the chymotrypsin inhibitor in potato, the kidney bean inhibitor, and the trypsin inhibitor in lima beans.
Type A antinutritives are substances primarily interfering with the digestion of proteins or the absorption and utilization of amino acids. They are also known as antiproteins. Strict vegetarians, for example, are in danger of nutritional inadequacy by this type of antinutritive. The most important type A antinutritives are protease inhibitors and lectins.
Protease inhibitors, occurring in many plant and animal tissues, are proteins that inhibit proteolytic enzymes by binding to the active sites of the enzymes. Proteolytic enzyme inhibitors were first found in avian eggs around the turn of the century. They were later identified as ovomucoid and ovoinhibitor, both of which inactivate trypsin. Chymotrypsin inhibitors also are found in avian egg whites. Other sources of trypsin or chymotrypsin inhibitors are soybeans and other legumes and pulses, vegetables, milk and colostrum, wheat and other cereal grains, guar gum, and white and sweet potatoes. The protease inhibitors of kidney beans, soybeans, and potatoes can additionally inhibit elastase, a pancreatic enzyme acting on elastin, an insoluble protein in meat. Animals, fed with food containing active inhibitors, show growth depression. This appears to be due to interference in trypsin and chymotrypsin activities and to excessive stimulation of the secretory exocrine pancreatic cells, which become hypertrophic. Valuable proteins may be lost to the feces in this case.
In vitro experiments with human proteolytic enzymes have been shown that trypsin inhibitors from bovine colostrum, lima beans, soybeans, kidney beans, and quail ovomucoid were active against human trypsin, whereas trypsin inhibitors originating from bovine and porcine pancreas, potatoes, chicken ovomucoid, and chicken ovoinhibitor were not. The soybean and lima bean trypsin inhibitors are also active against human chymotrypsin. Many protease inhibitors are heat labile, especially with moist heat. Relatively heat-resistant protease inhibitors include the antitryptic factor in milk, the alcohol-precipitable and nondialyzable trypsin inhibitor in alfalfa, the chymotrypsin inhibitor in potato, the kidney bean inhibitor, and the trypsin inhibitor in lima beans.
No comments:
Post a Comment
We hate SPAM!