Rennin
Title: Rennin
CAS Registry Number: 9001-98-3
Additional Names: Chymosin; rennase; lab; abomasal enzyme; Lab Ferment (German)
Literature References: Mol wt about 31,000. The predominant milk-clotting enzyme from the true stomach or abomasum of the suckling calf: Tauber, Kleiner, J. Biol. Chem. 96, 745 (1932). Secreted as an inactive precursor called prorennin and converted in the acid environment of the stomach to the active enzyme. Obtained by extracting dried strips of calf stomach with 5 to 10% NaCl soln contg boric acid for 5 days; improved process: Keil, US 2339931 (1942). Structure consists of a single polypeptide chain with internal disulfide bridges. Amino acid composition: Schwander et al., Helv. Chim. Acta 35, 553 (1952). Determn of N-terminal amino acid sequence: Foltmann, Philos. Trans. R. Soc. London 257B, 147 (1970). Homologies in amino acid sequences of rennin and pepsin: Tang, Hartley, Biochem. J. 118, 611 (1970). Reviews: Berridge, Adv. Enzymol. 15, 423 (1954); Foltmann, Milk Proteins 2, 217 (1971).
Properties: Yellowish powder, grains or scales. Peculiar, not unpleasant odor. Characteristic, slightly salty taste. Slightly hygroscopic. Can be purified enough to crystallize. The dry substance (sometimes diluted with NaCl or lactose) is stable, aq solns are not. Partially sol in water, dil alcohol. Insol at pH values near its isoelectric point of pH 4.5. pH of aq soln 5.8 (acceptable range 5.3-6.3). Strongly affected by ultraviolet (sunlight). Causes milk to coagulate, optimum temp 37-43°, optimum pH of milk 5.8. Not active below 15° nor above 55°. When a commercial prepn is labeled 1:10,000 it means that one gram will curdle 10 liters of milk at 35° within 40 minutes. Other strengths are 1:100,000 to 1:7,600,000.
Use: Rennet (a dried extract contg rennin) is used in the manuf of cheese and rennet casein, also sold retail for the making of junket or rennet custards.
Therap-Cat: Digestive enzyme.
Keywords: Digestive Aid; Enzyme; Digestive.

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