Chymosin A from Escherichia coli K-12 containing the Prochymosin A Gene

Prepared at the 53rd JECFA (1999) and published in FNP 52 Add 7 (1999), superseding tentative specifications prepared at the 37th JECFA (1990),
published in FNP 52 (1992). ADI "Not specified" established at the 37th JECFA in 1990.
SYNONYMS Rennin, milk-clotting enzyme, chymosin, chymosin A, aspartyl protease
C.A.S. number 84484-18-4
SOURCES Produced intracellularly by the controlled fermentation of Escherichia coli K-12 containing the bovine prochymosin A gene. The strain is non-pathogenic and non-toxicogenic (for example, JA198). Prochymosin is liberated by cell disruption followed by harvesting of the prochymosin by centrifugation or membrane concentration and washing with buffer solution. The residual production cells are inactivated by acid treatment, then the prochymosin is dissolved in buffer solution and after pH adjustment the solution is filtered. Prochymosin is activated to chymosin by acid treatment, followed by final purification via anion-exchange chromatography and elution with a buffered salt solution.
Active principles Chymosin
Systematic names and numbers
None (EC 3.4.23.4)
Reactions catalyzed Cleaves a single bond in kappa-casein
DESCRIPTION Clear, colourless or slightly coloured aqueous solution containing the active enzyme; preparations may contain caramel colour to facilitate their identification in cheese manufacture.
FUNCTIONAL USES Enzyme preparation
Used in clotting of milk for cheese production
GENERAL SPECIFICATIONS
Must conform to the General Specifications for Enzyme Preparations used in Food Processing (see Volume Introduction)