Enzymes rennin

The volume of extracellular fluid is direcdy related to the Na" concentration which is closely controlled by the kidneys. Homeostatic control of Na" concentration depends on the hormone aldosterone. The kidney secretes a proteolytic enzyme, rennin, which is essential in the first of a series of reactions leading to aldosterone. In response to a decrease in plasma volume and Na" concentration, the secretion of rennin stimulates the production of aldosterone resulting in increased sodium retention and increased volume of extracellular fluid (51,55). 

Even though casein micelles are remarkably stable in milk under normal conditions, they are quite susceptible to minor alterations in pH, ionic composition and to treatment with the enzyme rennin which cleaves the glycomacropeptide (GMP) portion of the k-... 

Limited digestion of the globular soy proteins (Harosoy variety) with the enzyme rennin affords a modified protein preparation which retains a high molecular weight. The enzyme-modified protein is precipitated and washed with alcohol and subsequently heat-modified. A flavorless product results which is easily dispersed in water and shows excellent functional characteristics. 

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. 

Derivation Acid casein warm skim milk is acidified with dilute sulfuric, hydrochloric, or lactic acid, the whey drawn off, and the curd washed, pressed, ground, and dried. Rennet casein warm skim milk is treated with an extract of the enzyme rennin (rennet). The curd contains combined calcium and calcium phosphate. 

An increase in both the yield and activity of the enzyme rennin from milk has been achieved using ultrasound [60]. Rennin is an important material used in the production of cheese. 

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. 

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. 

Rennet casein is somewhat different from acid-precipitated casein and it is a relatively minor industrial product. It is obtained from skim milk by the action of the enzyme rennin (chymosin) around pH 6.6. The enzyme splits up the casein component and this destabilises the milk micelles. This is followed by aggregation and precipitation of calcium caseinate along with the calcium phosphate which is present. 

A clear liquid secreted by the wall of the stomach. It contains hydrochloric acid and the enzymes rennin, pepsin, and gastric lipase. 

An extract of the stomach of certain mammals, which contains the enzyme rennin. It is used in making most cheeses and junkets. 

Rennet Casein n A type of casein precipitated from milk to means of rennet, the dried extract of stomach secretions from calves or other ruminants containing the enzyme rennin. See also Casein and Casein Plastic. 

Separation of Caseinogen by Bennin.— To 5 ml. of milk add 5-10 drops of an active preparation of the enzyme rennin, obtained from the gastric mucosa of calves. Mix and incubate at 40°. In a few minutes the milk will solidify owing to the conversion of caseinogen into insoluble casein (paracasein), and the tube may be inverted without spilling the contents. 

Bulk Enzymes. Enzymes such as proteases, amylases, glucose isomerases, and rennin are used in food processing. Similarly proteases and Hpases are used in detergents. CeUulases and xylanases are used in the paper pulp industry. The genes for most of the enzymes used in the various commercial processes have been cloned and overexpressed. Rennin (chymosin) produced from E. coli and A. nigerhas been approved by FDA for use in the dairy industry. 

The second enzyme to be crystallized (byjohn Nordrrnp in 1930). Even more than nrease before it, pepsin. study by Northrnp established tirat enzyme activity comes from proteins. fAiso known as rennin, it is tire major pepsinlike enzyine in gastric Jnice of fetal and newborn animals. 

The carboxyl proteases are so called because they have two catalytically essential aspartate residues. They were formerly called acid proteases because most of them are active at low pH. The best-known member of the family is pepsin, which has the distinction of being the first enzyme to be named (in 1825, by T. Schwann). Other members are chymosin (rennin) cathepsin D Rhizopus-pepsin (from Rhizopus chinensis) penicillinopepsin (from Penicillium janthinel-lum) the enzyme from Endothia parasitica and renin, which is involved in the regulation of blood pressure. These constitute a homologous family, and all have an Mr of about 35 000. The aspartyl proteases have been thrown into prominence by the discovery of a retroviral subfamily, including one from HIV that is the target of therapy for AIDS. These are homodimers of subunits of about 100 residues.156,157 All the aspartyl proteases contain the two essential aspartyl residues. Their reaction mechanism is the most obscure of all the proteases, and there are no simple chemical models for guidance. 

Specialized cells, called the juxtaglomerular apparatus (JGA), within the renal cortex are able to detect a fall in blood pressure and respond by secreting a proteolytic enzyme called renin (not to be confused with rennin). The substrate for renin, a liver-derived peptide called angiotensinogen, circulates in the plasma. Renin removes two amino acids from the N-terminal to produce angiotensin I, which is itself a substrate for angiotensin-converting enzyme (ACE). ACE removes two more amino acids to produce angiotensin II. 

Like captopril, enalapril selectively suppresses the rennin-angiotensin-aldosterone system, inhibits angiotensin-converting enzyme, and prevents conversion of angiotensin I into angiotensin 11. 

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. 

Cheese is a concentrated dairy food produced from milk curds that are separated from whey. The curds may be partially degraded by natural milk or microbial enzymes during ripening, as in cured cheeses, or they may be consumed fresh, as in uncured cheeses like cottage cheese. Most commonly, a bacterial culture with the aid of a coagulating enzyme like rennin is responsible for producing the initial curd. The... 

Abdel-Fattah, A. F., and Ismail, A. M. S. 1984. Production of rennin-like enzyme by Absidia cylindrospora. Agric. Wastes 11, 125-131. 

Abdel-Fattah, A. F., Mabrouk, S. S. and EL-Hawwary, N. M. 1972. Production and some properties of rennin-like milk-clotting enzyme from Penicillium citrinum. J. Gen. Microbiol. 70, 151-155. 

Castle, A. V. and Wheelock, J. V. 1972. Effect of varying enzyme concentration on the action of rennin on whole milk. J. Dairy Res. 39, 15-22. 

Foda, M. S. 1982. Characterization of rennin-like enzyme produced in submerged culture of Aspergillus niger. Egyptian J. Microbiol. 17, 105-114. 

Foda, M. S., Ismail, A. A. and Khorshid, M. A. 1975A. Production of a new rennin-like enzyme by Aspergillus Ochraceus. Milchwissenschaft 30, 598-601. 

Larson, M. K. and Whitaker, J. R. 1970. Endothiaparasitica protease, parameters affecting activity of the rennin-like enzyme. J. Dairy Sci. 53, 253-269. 

Richardson, G. H., Nelson, J. H., Lubnow, R. E. and Schwarberg, R. L. 1967. Rennin-like enzyme from Mucor pusillus for cheese manufacture. J. Dairy Sci. 50, 1066-1072... 

Microbial proteinases can be classified by mechanism of action. Hartley (1960) divided them into four groups serine proteinases, thio proteinases, metalloproteinases, and acid proteinases. Morihara (1974) classified enzymes within these groups according to substrate specificity. Enzymes which split peptide substrates at the carboxyl side of specific amino acids are called carboxyendopeptidases, and those which split peptide substrates at the amino side of specific amino acids are called aminoendopeptidases. Acid proteinases, such as rennin and pepsin, split either side of specific aromatic or hydrophobic amino acid residues. The action of proteolytic enzymes on milk proteins has been reviewed by Visser (1981). 

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. 

PROTEASE. A proteolytic enzyme that weakens or breaks the peptide linkages in proteins, They include some of the more widely known enzymes such as pepsin, trypsin, ficin, bromelm, papain, and rennin. Being water soluble they solubilize proteins and are commercially used for meat tendenzers, bread baking, and digestive aids. 

Originally enzymes were given nondescriptive names such as rennin curding of milk to start cheese-making processcr pepsin hydrolyzes proteins at acidic pH trypsin hydrolyzes proteins at mild alkaline pH... 

These products are biologically significant as some of these phosphonates have been observed to be potent inhibitors of proteolytic enzymes such as rennin and HIV protease. Stereoselective reduction of aminoketophosphonates using catecholborane provides a facile access to these biologically important molecules. 

Rennet Also known as rennin and chymosin. Enzyme that is used for curdling milk and making cheese. 

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