Other Products. Home Pepsin Pepsin. Pepsin is one of the principal protein degrading or proteolytic enzymes in the digestive system. During the process of digestion, Pepsin acts on the complex dietary protein and breaks up into peptides and amino acids which can be readily absorbed by the intestinal lining.
It helps in digestive disturbance in general and as a result of impaired production of gastric juice. It acts as an adjunct in the treatment of anemic conditions, especially during slimming diet when protein intake increases.
It is used as research tool in protein analysis and as digestive syrup in heart burn, acid indigestion and sour stomach. It is also used in tablets for increasing appetite and in the preparation of cheese and other protein-containing foods. Catalog NATE Catalog EXWM ProductName pepsin A.
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Cancer Research Infrastructure. The hormone, among other functions, stimulates exocrine pancreas to secrete a juice rich in enzymes present as zymogens , that is:. Therefore, in the duodenum there is a neutral environment rich in enzymes able to continue, once activated , protein digestion.
Moreover, as the proteases have different substrate specificity, each peptide produced by an enzyme can be substrate of another enzyme. In pancreatic juice, amylase, lipase and nuclease are also present.
The first and master step in their activation is the conversion of trypsinogen to trypsin by enteropeptidase also called enterokinase , an endopeptidase produced by cells of the duodenum after cholecystokinin stimulation. Enteropeptidase catalyses the cleavage of a specific peptide bond between a lysine residue and an isoleucine residue of the trypsinogen, with release of a hexapeptide. This causes a conformational rearrangement of the protein that activates it, that is, trypsin is formed.
The enzyme cleaves peptide bonds adjacent to lysine and arginine residues of protein to digest; moreover, it can activate chymotrypsinogen, proelastase and procarboxypeptidase A and B, but also other molecules of trypsinogen, like pepsin autocatalysis. Therefore, the ability of the duodenum to digest proteins increases as the pancreatic zymogens are activated, all triggered by a small amount of enteropeptidase.
Chymotrypsin acts on peptide bonds adjacent to phenylalanine, tryptophan, methionine, tyrosine and leucine residues. Proelastase is activated to elastase by the removal of a small peptide from the N-terminal end. Elastase, which is less specific than the other digestive hydrolases, catalyzes the cleavage of peptide bonds adjacent to amino acids such as glycine, alanine and serine.
Procarboxypeptidase Procarboxypeptidase A is activated to carboxypeptidase A; the protease cleaves peptide bonds adjacent to amino acids with branched or aromatic side chains, such as phenylalanine and valine. Procarboxypeptidase B is activated to carboxypeptidase B, specific for amino acids with basic side chains, such as lysine and arginine. The above-mentioned proteases, unlike pepsin, have an optimum pH of action ranging from7 to 8, that is, neutral or weakly alkaline.
The molecule, present in the pancreatic zymogen granules, is capable of binding very tightly the active site of the enzyme inactivating it. In this way, the activity of any trypsin resulting from a premature activation of trypsinogen is blocked, preventing a situation in which a few activated molecules activate all the pancreatic zymogens. In plants, there are many molecules with similar activity. An example is the Kunitz trypsin inhibitor, a protein mainly found in soybeans, that forms a very stable complex with the active site of trypsin.
Since the above-mentioned proteases have a distinct substrate specificity, acting on peptide bonds adjacent to different amino acids, each peptide generated by a protease can be substrate of another one. In this way the partially digested proteins that enter the duodenum are efficiently hydrolyzed into free amino acids and peptides of residues. These peptides are substrates of aminopeptidases secreted from enterocytes and associated with their microvilli.
Bile Juice 2. Pancreatic Juice 3. Intestinal Juice. Bile juice is secreted by the gall bladder. After being secreted by the gall bladder it travels through the bile duct that opens into the duodenum. Bile juice contains bile salt that helps to emulsify fats. Fats are broken down into small globules that are easily digested by the enzyme lipase present in the pancreatic juice. The pancreatic juice is secreted by the pancreas.
It travels through the pancreatic duct that opens into the duodenum. The enzymes present in the pancreatic juice are as follows:. The walls of the ilium are made up of fingerlike projections known as villi. Villi are made of up microvilli. Therefore, ilium has a very large surface area. The main function here is to absorb Vitamin B12, bile salts, and the products of digestion. Cells lining the ilium also secrete protease and carbohydrase enzymes responsible for the final stages of protein and carbohydrate digestions.
The villi contain large numbers of capillaries which take the amino acids and glucose produced by digestion to the liver through the hepatic portal vein. Lacteals are small lymph vessels that are present in villi.
They absorb fatty acids and glycerol, the products of fat digestion. The lacteals transport the fatty acids and glycerol to the lymphatic system for filtering. The fatty acids and glycerol are combined with the blood as lymph joins blood at the right and left subclavian veins.
The large intestine is mainly responsible for storing waste, reclaiming water, maintaining the water balance, and absorbing some vitamins, such as vitamin K.
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