Calf chymosin

The gene for calf chymosin has been cloned in Kluyveromyces marxianus var. lactis, Aspergillus niger and E. coli. Microbial (cloned) chymosins have... 

Green, M. L., Angal, S., Lowe, P. A. and Marston, F. A. O. 1985. Cheddar cheesemaking with recombinant calf chymosin synthesized in Escherichia coli. J. Dairy Res. 52, 281-286. 

Fig. 16.2. A section of the alignment of sequences of aspartic proteinases achieved by comparing the three-dimensional structures using COMPARER [14]. HIV human immunodeficiency virus RSV Rous sarcoma virus APE endothiapepsin APP penicillopepsin APR rhizopuspepsin PEP hexagonal porcine pepsin CHY calf chymosin. The last letter refers to the amino (N) or car-boxy (C) terminal domains of the pepsins. The coordinates of the three-dimensional structures were obtained from the PDB databank [24]. The amino acid code is the standard one-letter code (see Appendix C) formatted using the following conventions [7] ...

The residues Phe and Met are not intrinsically essential for chymosin action. Replacement of Phe by Phe (NO2) or cyclohexylamine reduces k J K 3- and 50-fold, respectively (Visser et al, 1977). Oxidation of Metioe reduces kcJKm 10-fold but substitution of norleucine for Met increases this ratio 3-fold. Neither porcine nor human K-casein possesses a Phe-Met bond [both have a Phe-Ile bond at this position (Brignon et al, 1985 Chobert et al, 1976 Fiat et al, 1977)], yet both are readily hydrolyzed by calf chymosin, although more slowly than bovine K-casein in contrast, porcine milk is coagulated more effectively than bovine milk by porcine chymosin (Foltmann, 1987). Thus, the sequence around the Phe-Met bond, rather than the bond itself, contains the important determinants for hydrolysis. The particularly important residues are Ser jo4, the hydrophobic residues Leuio3 and Ileiog, at least one of the three histidines (residues 98, 100, or 102), some or all of the four prolines (residues 99, 101, 109, and 110), and Lysiii. 

Chicken pepsin is the least suitable of these and is used widely only in Israel. Bovine pepsin is probably the most satisfactory and many commercial calf rennets contain up to 50% bovine pepsin its proteolytic specificity is generally similar to that of calf chymosin. The proteolytic specificities of the three principal fungal rennets are considerably different from that of calf chymosin but the acceptability of most cheese varieties made using fungal rennets is fairly good. Microbial rennets are widely used in the United States but to only a limited extent in Europe. The extensive literature on rennet substitutes has been reviewed by Sardinas (1972), Emstrom and Wong (1974), Nelson (1975), Green (1977), and Phelan (1985). 

It is generally accepted that calf chymosin produces the best quality cheese. An adequate supply of chymosin from genetically engineered microorganisms is now available and therefore rennet quality should not be a factor in cheese quality. 

Bines, V. E., Young, P., and Law, B. A. (1989). Comparison of cheese made with a recombinant calf chymosin and with standard calf rennet. J. Dairy Res. 56,657-664. 

Dobson MJ, Roberts NA, Tuite ME et al. (1983) Efficient synthesis of enzymatically active calf chymosin in Saccharomyces cerevisiae. Gene 24(1) 1-14 Doelle HW (1994) Microbial process development. World Scientific, Singapore, pp 241-276 Doha SC, Gaikar VG (2006) Aqueous to-phase partitioning of glucose isomerase from Actino-planes missouriensis in the presence of PEG-derivatives and its immobilization on chitosan beads. Separ Sci Technol 41(12) 2807-2823... 

Morris HJA, Anderson K (1991) A comparative study of Cheddar cheeses made with fermentation produced calf chymosin from Kluyveromyces lactis and with calf rennet. Cult Dairy Prod J... 

Tsuchiya K, Gomi K, Kitamoto K et al. (1993) Secretion of calf chymosin from the filamentous fungus Aspergillus oryzae. Appl Microbiol Biotechnol 40(2-3) 327-332 Tucker GA, Woods LFJ (1995) Enzymes in food processing. Blackie Academic Professional,... 

Proteinases with a pH-optimum of general proteolytic activity at pH below 6 are called acidic proteinases. Such enzymes were at first recognized as the proteinases of the vertebrate gastric juice, and for many years porcine pepsin and calf chymosin have been the most well-known members of this group. 

Calf prochymosin, calf chymosin (calf prochym., calf chym.). NH2-terminus of the active enzyme is Gly-45. Residues 1-105 (60,61). S-S bridges and residues 357-373 (7). The rest of the sequence from Foltmann and coworkers unpublished results. Residue 290 is aspartic acid in chymosin A and glycine in chymosin B. 

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