Stomach rennin

Although acid caseins are employed for a number of purposes, rennet caseins in which the protein remains associated with calcium and phosphate are preferred for plastics applications. Rennet is the dried extract of rennin, obtained from the inner lining of the fourth stomach of calves, and is a very powerful coagulant. As little as 0.2 parts per million are said to be sufficient to coagulate slightly acidic milk. Its coagulating power is destroyed at 100°C. 

The first company based upon applied biocatalysis also dates back to the 19 century. In 1874 Christian Hansen started a company in Copenhagen, Denmark. His company— named Christian Hansen s Laboratory to this day—was the first in the industrial market with a standardized enzyme preparation, rennet, for cheese making. Rennet, a mixture of chymosin (also called rennin) and pepsin, was and still is obtained by salt extraction of the fonrth stomach of suckling calves. 

Casein is not coagulated by heat. It is precipitated by acids and by rennin. a proteolytic enzyme obtained from the stomach or calves. Casein is a conjugated protein belonging lo the group uf phosphoproteins. The enzyme trypsin can hydrolyze off a phosphorus-containing peptone. 

Rennet or rennin—an animal prolease derived from the stomachs of calves as well as from microorganisms. Rennet is used in the manufacture of cheese to clot milk. 

In the stomach, the chemicals contact other already-existing materials (stomach contents), secretions, (e.g., pepsin, gastric lipase, rennin), and hydrochloric acid. The effect of pH in the stomach, and the influence of pH on the ionization of weak organic acids and bases, plays a major role in the bioavailability of the chemical within the organism. 

Rennin Not known Stomach Not known Not known Removes glycopeptide from K-casein... 

The stomach environment is acidic as a result of HC1 secretion by the parietal cells. The acidic pH serves to denature many proteins, thus making them susceptible to proteolysis. The chief cells of the stomach produce pepsinogen, which is activated to pepsin by the HC1 (see Table 20.3). The optimum pH of peptic activity is around 2, and pepsin is inactivated at neutrality. Another stomach enzyme is rennin or chymosin, which is present in infants but not in adults. It removes a glycopeptide from milk-K-casein, disrupting the casein micelle and promoting milk protein coagulation and digestion. 

Milk Coagulation. The first step in cheese manufacture is the coagulation of milk. Traditionally, this coagulation step is catalyzed by the enzyme rennet. Rennet is a saline extract of the 4th stomach of calves, usually slaughtered before they are 30 days old. The principal protease in rennet is rennin. In an attempt to avoid confusion with the hormone peptide renin, the International Enzyme Nomenclature Committee has assigned the name chymosin to the protease in calf rennet. During the growth of calves, chymosin is replaced by pepsin, the acid protease of the mature stomach. 

Rennin is present in the fourth stomach of the suckling calf. It is secreted in an inactive form, a zymogen, named prorennin. The crude extract obtained from the dried stomachs (veils) contains both rennin and prorennin. The conversion of prorennin to rennin can be speeded up by addition of acid. This conversion involves an autocatalytic process, in which a limited proteolysis of the proren-... 

Q4 Water, mucus, pepsinogen and gastric lipase, which digests milk fats, are produced by the stomach. In young animals, rennin is also present in gastric secretions. The volume of secretion produced each day is approximately 21. 

The stomach also contains an enzyme, rennin, which assists in the digestion of milk, and another enzyme, lipase, which catalyzes the decomposition of fats into simpler substances. Additional enzymes involved in the digestion of polysaccharides, proteins, and fats take part in the continuation of the digestion in the intestines these enzymes are contained in the intestinal juice, pancreatic juice, and bile. 

Rennin is absent from the human stomach, but is present in that of newborn calves (see D2). Since pepsin may perform rennins function, i.e., milk coagulation, rennin is superfluous in the stomach of man. 

A historical use of enzymes is the use of cow stomachs, containing the enzyme rennin, to curdle milk and initiate the cheese-making process. Enzymes are now applied commercially on both large and small scales. The three major categories for commercial production are industrial enzymes, analytical enzymes, and medical enzymes. Industrial enzymes are applied in tons, while analytical and medical enzymes are applied in the range of milligrams to grams. 

A proteolytic enzyme secreted by gastrie mueosa of infants is chymosin (rennin), which functions to clot milk and promote its digestion by preventing rapid passage from the stomach. Chymosin hydrolyzes casein, a mixture of several related milk proteins, to paracasein, whieh reacts with Ca + to yield the insoluble curd. Pepsin performs the same funetions as chymosin. Chymosin is found in the fourth stomach of ruminants. Calf stomach is a source of this enzyme, which is used in the manufacture of cheese. Chymosin has been synthesized by recombinant DNA techniques and successfully used in the produetion of cheese. 

Not to be confused with rennin, the milk-curdling enzyme found in the stomach of ruminant animals. 

Although the brush border disaccharid-ases (maltasc. lactase, sucrase) are present at birth, for the first 7 days of life lactose may be absorbed unchanged and appearin the urine in the normtd infant. The pR)teo-lytic enzymes, rennin and pepsin, are present in the neonatal stomach, but some protein may be absorbed without digestion. 

At the beginning of this century, Sawyalow gave the name plastein to the insoluble material which appeared upon the incubation of a soluble mixture of enzymatic digestion products of fibrin with rennin (a pepsin-like enzyme from calf-stomach). This reaction, later observed also with enzymes different from rennin was studied more intensively in the 1920s by Wasteneys and Borsook [29] who showed that the products of peptic hydrolysis of egg albumin at pH 1.6 gradually formed a precipitate when the concentrated solution was incubated with pepsin at pH 4. 

Definition A dried extract containing rennin, the milk-clotting enzyme from calf stomach... 

To produce artificial horn, skimmed milk is treated at 35° C with fermenting rennin from the stomachs of calves. When the temperature is raised to 65° C, coagulation of the protein results (denaturing) with the formation of curds containing about 609 /water. They are washed, dried, and pressed in linen bags. Alternatively, the protein can also be precipitated with acids. About 1 kg of dried casein is obtained from 30 liters of skimmed milk. The commercial product contains fat and therefore has a milky yellow color. 

Rennin Calf stomach lining Rennin Aqueous NaCI ... 

Rennin An enzyme from calves stomachs used in cheese manufacture. 

Cellulases, pectinases Rennin, derived from the stomachs of young ruminant animals Lipases... 

---