Natural heterogeneity of chymosin and pepsin in extracts of bovine stomachs

The two main components, chymosin and pepsin, in calf and adult bovine rennet show heterogeneity with respect to their charge and activity. A large number of single stomachs have been extracted and their isoenzymes have been analysed by HPLC. The results showed three genetic forms of chymosin A, B and C and these are present in individual stomachs in the following combinations: AA, BB, CC, AB, AC and BC. The C variant, which can be distinguished from the degradation product of chymosin A, has never been characterised before. All three chymosins have been purified and partially characterised. Also bovine pepsins show a natural variability: the ratio between the main pepsin fractions varies according to the age of the animal and it therefore provides a criterion to distinguish between pepsin from calf and adult bovine animals.