Pepsin is constructed with an extra 44 amino acids, shown in green in the lower illustration from entry 3psg , which block the large active site groove and hobble the enzyme. In the stomach, this extraneous chain is clipped off and the enzyme begins its destructive campaign. For several reasons, digestive enzymes are attractive candidates for scientific study.
They are easily isolated and present in large amounts in digestive juices. They are also extraordinarily stable, because they perform their jobs under the harsh conditions present in the digestive system.
The reactions catalyzed by digestive enzymes are also easily followed: you can add them to a protein such as gelatin and watch it lose its gel-like consistency.
In the 18th century, pepsin was the first enzyme to be discovered, and later, pepsin was the second enzyme to be crystallized after urease. These crystals played an important role in showing that enzymes were proteins and that they had a defined structure. Today, the structure of pepsin, determined from similar crystals, is available in PDB entry 5pep and several others.
Acid proteases: pepsin upper left , chymosin upper right , cathepsin D lower left , and endothiapepsin lower right.
Pepsin is one example of a group of enzymes termed "acid proteases. Pepsin works its best in strong hydrochloric acid. But the similarity with the other enzymes pictured here refers to a second type of acid.
The active site of the acid proteases rely on two acidic aspartate amino acids, which activate a water molecule and use it to cleave protein chains. These aspartates are pictured on the next page. The acid proteases have evolved to fill several functional roles in different organisms. Pepsin, shown at upper left PDB entry 5pep , is optimized for digestion of food in the acidic environment of the stomach.
It is very promiscuous, cleaving proteins in many different places. Sucralfate can also inhibit pepsin activity. Pepsin can be used in the food industry. Pepsin is a component of pancreatic curd that condenses and twists during cheese production.
Pepsin can be used to modify soybean protein and gelatin and provide whipping qualities. It can also modify the plant protein used in non-dairy snacks and make pre-cooked cereals into instant hot cereals. Pepsin can also be used to prepare animal and plant protein hydrolysates for seasoning food and beverages.
In the leather industry, it is used to remove hair and residual tissue from leather and to recover silver from abandoned photographic film by digesting the gelatin layer in which silver is stored. Website Search Exact Search Search. Plant Extracts. Mushroom Extracts. Animal Extracts. Fruit Powder. Vegetable Powder. Vegetarian Protein. 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. Hydrochloric Acid HCl 2. Renin 3. Pepsinogen 4. Gelatinase 5.
Gastric Amylase 6. Gastric Lipase. HCl keeps the stomach pH acidic. As HCl is a strong acid, it will kill most of the bacteria present in the food. It has another main function. That is to convert pepsinogen into pepsin.
Pepsinogen is activated by HCl into Pepsin. Pepsin digests other proteins present in the food to smaller peptides fragments. Gelatinase digests type I and type V gelatin and type IV and V collagen, which are proteoglycans in the meat.
These are all the digestive processes that take place in the stomach. The remaining food, now called chyme, is passed through the abdomen into the duodenum through the pyloric sphincter present at the lower end of the abdomen.
The main function of this gland is to produce an alkaline solution contain bicarbonate ion in order to : 1. To protect the duodenum from the acidic content of chyme 2. To provide an alkaline condition for the intestinal enzymes to be active, thus enabling absorption to take place 3. To lubricate intestinal walls. There are also 3 juices secreted in the Duodenum: 1. 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.
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